Powering and/or charging with more than one protocol

ABSTRACT

Systems and methods for modifying the magnitude and/or phase of an electromagnetic field in one or multiple dimensions. Applications for use in charging or powering multiple devices with a wireless power charger system are also described. Applications include beam shaping, beam forming, phase array radar, beam steering, etc. and inductive charging and power, and particularly usage in mobile, electronic, electric, lighting, or other devices, batteries, power tools, kitchen, industrial applications, vehicles, and other usages. Embodiments of the invention can also be applied generally to power supplies and other power sources and chargers, including systems and methods for improved ease of use and compatibility and transfer of wireless power to mobile, electronic, electric, lighting, or other devices, batteries, power tools, kitchen, military, industrial applications and/or vehicles.

CLAIM OF PRIORITY AND CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/522,506, titled “INDUCTIVE POWERING AND/OR CHARGING WITH MORE THANONE POWER LEVEL AND/OR FREQUENCY,” filed Nov. 9, 2021, which is acontinuation of U.S. patent application Ser. No. 16/199,904, titled“POWERING AND/OR CHARGING WITH MORE THAN ONE PROTOCOL,” filed Nov. 26,2018, and subsequently issued on May 24, 2022 as U.S. Pat. No.11,342,777, which is a continuation-in-part of U.S. patent applicationSer. No. 14/929,315, titled “POWERING AND/OR CHARGING WITH A PLURALITYOF PROTOCOLS,” filed Oct. 31, 2015, and subsequently issued on Nov. 27,2018 as U.S. Pat. No. 10,141,770, which is a continuation-in-part ofU.S. patent application Ser. No. 13/352,096, titled “SYSTEMS AND METHODSFOR PROVIDING POSITIONING FREEDOM, AND SUPPORT OF DIFFERENT VOLTAGES,PROTOCOLS, AND POWER LEVELS IN A WIRELESS POWER SYSTEM,” filed Jan. 17,2012, and subsequently issued on Nov. 3, 2015 as U.S. Pat. No.9,178,369, which application claims the benefit of priority to U.S.Provisional Patent Application No. 61/546,316, titled “SYSTEMS ANDMETHODS FOR PROVIDING POSITIONING FREEDOM, AND SUPPORT OF DIFFERENTVOLTAGES, PROTOCOLS, AND POWER LEVELS IN A WIRELESS POWER SYSTEM,” filedOct. 12, 2011; U.S. Provisional Patent Application No. 61/478,020,titled “SYSTEM AND METHOD FOR MODULATING THE PHASE AND AMPLITUDE OF ANELECTROMAGNETIC WAVE IN MULTIPLE DIMENSIONS,” filed Apr. 21, 2011; andU.S. Provisional Patent Application No. 61/433,883, titled “SYSTEM ANDMETHOD FOR MODULATING THE PHASE AND AMPLITUDE OF AN ELECTROMAGNETIC WAVEIN MULTIPLE DIMENSIONS,” filed Jan. 18, 2011, each of which applicationsare incorporated by reference in their entirety herein.

COPYRIGHT NOTICE

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent file or records, but otherwise reserves all copyrightrights whatsoever.

FIELD OF INVENTION

Embodiments of the invention are generally related to systems andmethods for modifying the magnitude and/or phase of an electromagneticfield in one or multiple dimensions. Applications for use in charging orpowering multiple devices with a wireless power charger system are alsodescribed.

BACKGROUND

Wireless technologies for powering and charging mobile and otherelectronic or electric devices, batteries and vehicles have beendeveloped. These systems generally use a wireless charger or transmittersystem, and a wireless receiver in combination, to provide a means fortransfer of power across a distance. For safe and efficient operation ofbasic wireless charging systems, the two coil parts of the system aretypically aligned and of comparable or similar size. Such operationtypically requires the user to place the device or battery to be chargedin a specific location with respect to the charger. To enable betterease of use, it is desirable that the receiver can be placed on a largersurface area charger without the need for specific alignment of theposition of the receiver. It is further desirable to be able to chargeor power multiple devices of similar or different power and voltagerequirements or operating with different wireless charging protocols onor near the same surface. These are the general areas that embodimentsof the invention are intended to address.

SUMMARY

Described herein are systems and methods of modulating the phase andamplitude of an electromagnetic field in one or multiple (e.g. one, twoor three) dimensions. Applications include beam shaping, beam forming,phase array radar, beam steering, etc. and inductive charging and power,and particularly usage in mobile, electronic, electric, lighting, orother devices, batteries, power tools, kitchen, industrial applications,vehicles, and other usages. Embodiments of the invention can also beapplied generally to power supplies and other power sources andchargers, including systems and methods for improved ease of use andcompatibility and transfer of wireless power to mobile, electronic,electric, lighting, or other devices, batteries, power tools, kitchen,military, industrial applications and/or vehicles.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates an exemplary charger and receiver, in accordance withan embodiment.

FIG. 2 illustrates an exemplary circuit, in accordance with anembodiment.

FIG. 3 illustrates another exemplary circuit, in accordance with anembodiment.

FIG. 4 illustrates another exemplary circuit, in accordance with anembodiment.

FIG. 5 illustrates another exemplary circuit, in accordance with anembodiment.

FIG. 6 illustrates another exemplary circuit, in accordance with anembodiment.

FIG. 7 illustrates another exemplary circuit, in accordance with anembodiment.

FIG. 8 illustrates a typical battery charge cycle, in accordance with anembodiment.

FIG. 9 illustrates a typical wireless power system operation, inaccordance with an embodiment.

FIG. 10 illustrates a communication process and regulation of powerand/or other functions, in accordance with an embodiment.

FIG. 11 illustrates configurations for a tightly coupled power transfersystem with individual transmitter coils of different size, inaccordance with an embodiment.

FIG. 12 illustrates a coil, in accordance with an embodiment.

FIG. 13 illustrates a resulting calculated magnetic field, in accordancewith an embodiment.

FIG. 14 illustrates the resonance in power transfer, in accordance withan embodiment.

FIG. 15 illustrates the magnetization curves of a number ofFerromagnetic materials, in accordance with an embodiment.

FIG. 16 illustrates the hysteresis curve for a hard ferromagneticmaterial such as steel, in accordance with an embodiment.

FIG. 17 illustrates the real and imaginary part of the permeability of aferromagnetic material layer, in accordance with an embodiment.

FIG. 18 illustrates the magnetization curves of a high permeabilityproprietary soft magnetic ferrite material, in accordance with anembodiment.

FIG. 19 illustrates a large area transmitter coil covered by aferromagnetic, ferrite, or other magnetic material, in accordance withan embodiment.

FIG. 20 illustrates the use of a ferrite magnetic material or switchinglayer above the coil to guide and shield the flux, in accordance with anembodiment.

FIG. 21 illustrates the use of Litz wire wrapped around the core tocreate a solenoid type receiver, in accordance with an embodiment.

FIG. 22 illustrates examples of magnets that can be used, in accordancewith an embodiment.

FIG. 23 illustrates a magnetic aperture by incorporating a permanentand/or electromagnet into the receiver, in accordance with anembodiment.

FIG. 24 illustrates magnetization curves of a soft ferrite material areshown at different operating temperatures, in accordance with anembodiment.

FIG. 25 illustrates a magnetic aperture geometry for receivers ofdissimilar size, in accordance with an embodiment.

FIG. 26 illustrates various multi-pole magnets, in accordance with anembodiment.

FIG. 27 illustrates various ring magnets, in accordance with anembodiment.

FIG. 28 illustrates examples of multi-pole ring or arc magnets with cutsor gaps in the circular pattern, in accordance with various embodiments,in accordance with an embodiment.

FIG. 29 illustrates a wire or cable available in a variety of gauges, inaccordance with an embodiment.

FIG. 30 illustrates a saturable reactor or magnetic amplifier, inaccordance with an embodiment.

FIG. 31 illustrates a configuration that includes a charger switchingmagnet, and optional charger and/or receiver shielding layers, inaccordance with an embodiment.

FIG. 32 illustrates a system that uses two coils for the charger and twofor the receiver, in accordance with an embodiment.

FIG. 33 illustrates a configuration where one or more repeaters areinserted between the charger and receiver resonant antennas, inaccordance with an embodiment.

FIG. 34 illustrates a layer comprising a magnetic or ferrite or othermaterial added to the charger to limit the emission from the chargerinto space, in accordance with an embodiment.

FIG. 35 illustrates the use of one or more repeater antennas and one ormore magnetic/switching layers, in accordance with an embodiment.

FIG. 36 illustrates another use of one or more repeater antennas and oneor more magnetic/switching layers, in accordance with an embodiment.

FIG. 37 illustrates a charger coil that is flat with a magnetic orswitching layer formed in the shape of a cup, cup holder cylinder orother bowl, in accordance with an embodiment.

FIG. 38 illustrates how the charger coil can be wrapped around thevertical cylinder body while the inside of the cup uses the magneticsolid material, layer or laminated film, in accordance with anembodiment.

FIG. 39 illustrates architectures where the charger circuit comprisessub circuits or units whereby each sub-unit is responsible for poweringor charging and/or communicating with one power receiver, in accordancewith an embodiment.

FIG. 40 illustrates a geometry where multiple transmitter coils coverdifferent areas of a multi-charger/power supply, in accordance with anembodiment.

FIG. 41 illustrates use of a magnetic layer and creation of magneticcoupling or a magnetic aperture, in accordance with an embodiment.

FIG. 42 illustrates a mobile device such as a mobile phone with areceiver coil and receiver circuit integrated into the back cover orbattery door, in accordance with an embodiment.

FIG. 43 illustrates a circuit wherein the charger includes capacitorsand switches, in accordance with an embodiment.

FIG. 44 illustrates a resonant converter architecture, in accordancewith an embodiment.

FIG. 45 illustrates a geo-cast architecture, in accordance with anembodiment.

FIG. 46 illustrates architectures for full positioning freedom, inaccordance with an embodiment.

FIG. 47 illustrates a multi-receiver system, in accordance with anembodiment.

FIG. 48 illustrates the use of multiple charger sections, in accordancewith an embodiment.

FIG. 49 illustrates a simplified system for wireless transmission ofpower with constant output voltage, in accordance with an embodiment.

FIG. 50 illustrates a system that includes a feedback channel, inaccordance with an embodiment.

FIG. 51 illustrates use of a variable inductor in parallel to thecharger and/or receiver coil, in accordance with an embodiment.

DETAILED DESCRIPTION

With the proliferation of electrical and electronic devices and vehicles(which are considered examples of devices herein), simple and universalmethods of providing power and or charging of these devices is becomingincreasingly important.

The term device, product, or battery is used herein to include anyelectrical, electronic, mobile, lighting, or other product, batteries,power tools, industrial, kitchen, military or medical products andvehicles or movable machines such as robots whereby the product, part,or component is powered by electricity or an internal or externalbattery and/or can be powered or charged externally or internally by agenerator or solar cell, fuel cell, hand or other mechanical crank oralike. A product or device can also include an attachable or integralskin, case, battery door or attachable or add-on or dongle type ofreceiver component to enable the user to power or charge the product ordevice.

In accordance with various embodiments, an induction power transmitteremploys a magnetic induction coil(s) transmitting energy to a receivingcoil(s) in a device or product, case, battery door, or attachable oradd-on component including attachments such as a dongle or a batteryinside or outside of device or attached to device through a connectorand/or a wire, or stand-alone placed near the power transmitterplatform. The receiver can be an otherwise incomplete device thatreceives power wirelessly and is intended for installation or attachmentin or on the final product, battery or device to be powered or charged,or the receiver can be a complete device intended for connection to adevice, product or battery directly by a wire or wirelessly.

As used herein, the term wireless power, charger, transmitter orinductive power and charger are used interchangeably. In accordance withan embodiment, the wireless charger may be a flat or curved surface orpart that can provide energy wirelessly to a receiver. It can also beconstructed of flexible materials and/or coils or even plasticelectronics to enable mechanical flexibility and bending or folding tosave space or for conformity to non-flat surfaces. The wireless chargermay be directly powered by an AC power input, DC power, or other powersource such as a car, motorcycle, truck or other vehicle or airplane orboat or ship power outlet, or vehicle, boat, ship or airplane itself,primary (non-rechargeable) or rechargeable battery, solar cell, fuelcell, mechanical (hand crank, wind source, etc.), nuclear source orother or another wireless charger or power supply or a combinationthereof. In addition, the wireless charger may be powered by a part suchas a rechargeable battery which is itself in turn recharged by anothersource such as an AC or DC power source, vehicle, boat or ship orairplane outlet or vehicle, boat or ship or airplane itself, solar cell,fuel cell, wind or mechanical (hand crank, wind, etc.) or nuclearsource, etc. or a combination thereof. In addition, in cases where thewireless charger is powered by a rechargeable source such as a battery,the battery can also be itself in turn inductively charged by anotherwireless charger. The wireless charger may be a stand-alone part,device, or product, or may be incorporated into another electric orelectronics device, table, desk chair, TV stand or mount or furniture orvehicle or airplane or marine vehicle or boat or objects such as atable, desk, chair, counter-top, shelving or check out or cashiercounters, kiosk, car seat, car console, car door, netting, cup holder,dashboard, glovebox, etc., airplane tray, computer, laptop, netbook,tablet, display, TV, magnetic, optical or semiconductor storage orplayback device such as hard drive, optical players, etc., cable or gameconsole, computer pads, toys, clothing, bags or backpack, belt orholster, etc., industrial, military or kitchen counter, area, devicesand appliances, phones, cameras, radios, stereo systems, etc. Thewireless charger may also have other functions built in or beconstructed such that it is modular and additionalcapabilities/functions can be added as needed.

Some of these capabilities/functions include an ability to providehigher power, charge more devices, exchange the top surface or exteriorbox or cosmetics, operate by internal power as described above throughuse of a battery and/or renewable source such as solar cells,communicate and/or store data from a device, provide communicationbetween the device and other devices or the charger and/or a network,etc. An example is a basic wireless charger that has the ability to beextended to include a rechargeable battery pack to enable operationwithout external power. Another example may be a wireless chargercontaining or one or more speakers and/or microphone and Bluetooth,WiFi, etc. connectivity as a module that would enhance the basic chargerto allow a mobile phone or music player being charged on the charger toplay/stream music or sound or carry out a hands free conversation overthe speakers and/or microphone wirelessly through a Bluetooth, WiFi, orother connection. Another example may be a charger product or computeror laptop, or display or TV etc. that also contains a disk drive, solidstate memory or other storage device and when a device is placed on thecharger, data connectivity through the charger, Bluetooth, NFC, Felica,WiFi, Zigbee, Wireless USB, etc. is also established for transfer,synchronizing or update of data or programs occurs to download/uploadinfo, display or play music or video or synchronize data. One exemplaryuse may be a camera or phone charger whereby many other combinations ofproducts and capabilities may be enabled in combination of charging andother functions. Examples of products or devices powered or charged bythe induction transmitter and receiver include but are not limited tobatteries, cell phones, smart phones, cordless phones, communicationdevices, personal data assistants, portable media players, globalpositioning (GPS) devices, Bluetooth headsets and other devices,shavers, watches, tooth brushes, calculators, cameras, optical scopes,infrared viewers, computers, laptops, tablets, netbooks, key boards,computer mice, book readers or email devices, pagers, computer monitors,televisions, music or movie players and recorders, storage devices,radios, clocks, speakers, gaming devices, game controllers, toys, remotecontrollers, power tools, construction tools, office equipment, robotsincluding vacuum cleaning robots, floor washing robots, pool cleaningrobots, gutter cleaning robots or robots used in hospital, clean room,military or industrial environments, industrial tools, mobile vacuumcleaners, medical or dental tools, military equipment or tools, kitchenappliances, mixers, cookers, can openers, food or beverage heaters orcoolers such as electrically powered beverage mugs, massagers, adulttoys, lights or light fixtures, or advertising applications, printers,fax machines, scanners, automobiles, buses, or other vehicles or mobiletransportation machines, and other battery or electrically powereddevices or products. The receiver or the charger could also beincorporated into a bag, carrier, skin, clothing, case, packaging,product packaging or box, crate, box, display case or rack, table,bottle or device etc. to enable some function inside the bag, carrier,skin, clothing, case, packaging, product packaging or box, crate, box,display case or rack, table, bottle (such as, e.g. causing a displaycase or packaging to display promotional information or instructions, orto illuminate) and/or to use the bag, carrier, skin, clothing, case,packaging, product packaging or box, crate, box, display case or rack,table, bottle, etc. to power or charge another device or componentsomewhere on or nearby. It is important to note that the product ordevice does not necessarily have to be portable and/or contain a batteryto take advantage of induction or wireless power transfer. For example,a lighting fixture or a computer monitor that is typically powered by anAC outlet or a DC power supply may be placed on a table top and receivepower wirelessly. The wireless receiver may be a flat or curved surfaceor part that can receive energy wirelessly from a charger. The receiverand/or the charger can also be constructed of flexible materials and/orcoils or even plastic electronics to enable mechanical flexibility andbending or folding to save space or for conformity to non-flat surfaces.

In accordance with various embodiments, many of these devices containinternal batteries, and the device may or may not be operating duringreceipt of power. Depending on the degree of charge status of thebattery or its presence and the system design, the applied power mayprovide power to the device, charge its battery or a combination of theabove. The terms charging and/or power are used interchangeably hereinto indicate that the received power can be used for either of thesecases or a combination thereof. Unless specifically described, theseterms are therefore used interchangeably. Also, unless specificallydescribed herein, in accordance with various embodiments the termscharger power supply and transmitter are used interchangeably.

As shown in FIG. 1, in accordance with an embodiment, a wireless chargeror power system 100 comprises a first charger or transmitter part, and asecond receiver part. The charger or transmitter can generate arepetitive power signal pattern (such as a sinusoid or square wave from10's of Hz to several MHz or even higher, but typically in the 100 kHzto several MHz range) with its coil drive circuit and a coil or antennafor transmission of the power. The charger or transmitter typically alsoincludes a communication and regulation/control system that detects areceiver and/or turns the applied power on or off and/or modify theamount of applied power by mechanisms such as changing the amplitude,frequency or duty cycle, etc. or a change in the resonant condition byvarying the impedance (capacitance or inductance) of the charger or acombination thereof of the applied power signal to the coil or antenna.In accordance with an embodiment, the charger can also be the whole orpart of the electronics, coil, shield, or other part of the systemrequired for transmitting power wirelessly. The electronics may comprisediscrete components or microelectronics that when used together providethe wireless charger functionality, or comprise an Application SpecificIntegrate Circuit (ASIC) chip or chipset that is specifically designedto function as the whole or a substantial part of the electronics forwireless charger system.

The second part of the system is a receiver that includes a coil orantenna to receive power, a method for change of the received AC voltageto DC voltage, such as rectification and smoothing with one or morerectifiers or a bridge or synchronous rectifier, etc. and one or morecapacitors. In cases where the voltage at the load does not need to bekept within a tight tolerance or can vary regardless of the loadresistance or the resistance of the load is always constant, therectified and smoothed output of the receiver can be directly connectedto a load. Examples of this situation may be in lighting applications,applications where the load is a constant resistance such as a heater orresistor, etc. In these cases, the receiver system could be quite simpleand inexpensive. In many other cases, the resistance or impedance of theload changes during operation. This includes cases where the receiver isconnected to a device whose power needs may change during operation orwhen the receiver is used to charge a battery. In these cases, theoutput voltage may need to be regulated so that it stays within a rangeor tolerance during the variety of operating conditions. In these cases,the receiver may optionally include a regulator such as linear, buck,boost or buck boost, etc. regulator and/or switch for the output power.Additionally, the receiver may include a method for the receiver tocommunicate with the charger. The receiver may optionally include areactive component (inductor or capacitor) to increase the resonance ofthe system and a switch to allow switching between a wired and wirelessmethod of charging or powering the product or battery. The receiver mayalso include optional additional features such as including Near FieldCommunication, Bluetooth, WiFi, RFID or other communication and/orverification technology.

The charger or transmitter coil and the receiver coil can have any shapedesired and may be constructed of PCB, wire, Litz wire, or a combinationthereof. To reduce resistance, the coils can be constructed of multipletracks or wires in the PCB and/or wire construction. For PCBconstruction, the multiple layers can be in different sides of a PCBand/or different layers and layered/designed appropriately to provideoptimum field pattern, uniformity, inductance, and/or resistance orQuality factor (Q) for the coil. Various materials can be used for thecoil conductor such as different metals and/or magnetic material orplastic conductors, etc. Typically, copper with low resistivity may beused. The design should also take into account the skin effect of thematerial used at the frequency of operation to preferably provide lowresistance.

The receiver can be an integral part of a device or battery as describedabove, or can be an otherwise incomplete device that receives powerwirelessly and is intended for installation or attachment in or on thefinal product, battery or device to be powered or charged, or thereceiver can be a complete device intended for connection to a device,product or battery directly by a wire or wirelessly. Examples includereplaceable covers, skins, cases, doors, jackets, surfaces, etc fordevices or batteries that would incorporate the receiver or part of thereceiver and the received power would be directed to the device throughconnectors in or on the device or battery or the normal wired connector(or power jack) of the device or battery. The receiver may also be apart or device similar to a dongle that can receive power on or near thevicinity of a charger and direct the power to a device or battery to becharged or powered through a wire and/or appropriate connector. Such areceiver may also have a form factor that would allow it to be attachedin an inconspicuous manner to the device such as a part that is attachedto the outer surface at the bottom, front, side, or back side of alaptop, netbook, tablet, phone, game player, or other electronic deviceand route the received power to the input power connector or jack of thedevice. The connector of such a receiver may be designed such that ithas a pass through or a separate connector integrated into it so that awire cable for providing wired charging/power or communication can beconnected to the connector without removal of the connector thusallowing the receiver and its connector to be permanently orsemi-permanently be attached to the device throughout its operation anduse. Many other variations of the receiver implementation are possibleand these examples are not meant to be exhaustive. In accordance with anembodiment, the receiver can also be the whole or part of theelectronics, coil, shield, or other part of the system required forreceiving power wirelessly. The electronics may comprise discretecomponents or microcontrollers that when used together provide thewireless receiver functionality, or comprise an Application SpecificIntegrate Circuit (ASIC) chip or chipset that is specifically designedto function as the whole or a substantial part of the electronics forwireless receiver system.

Optional methods of communication between the charger and receiver canbe provided through the same coils as used for transfer of power,through a separate coil, through an RF or optical link, through RFID,Bluetooth, WiFi, Wireless USB, NFC, Felica, Zigbee, Wireless Gigabit(WiGig), etc. or through such protocols as defined by the Wireless PowerConsortium (WPC) or other protocols or standards, developed for wirelesspower, or other communication protocol, or combination thereof.

In the case that communication is provided through the power transfercoil, one method for the communication is to modulate a load in thereceiver to affect the voltage in the receiver coil and therefore createa modulation in the charger coil parameters that can be detected throughmonitoring of its voltage or current. Other methods can includefrequency modulation by combining the received frequency with a localoscillator signal or inductive, capacitive, or resistive modulation ofthe output of the receiver coil.

The communicated information can be the output voltage, current, power,device or battery status, validation ID for receiver, end of charge orvarious charge status information, receiver battery, device, or coiltemperature, and/or user data such as music, email, voice, photos orvideo, or other form of digital or analog data used in a device. It canalso be a pattern or signal or change in the circuit conditions that istransmitted or occurs to simply notify the presence of the receivernearby.

In accordance with an embodiment, the data communicated can be any oneor more of the information detailed herein, or the difference betweenthese values and the desired value or simple commands to increase ordecrease power or simply one or more signals that would confirm presenceof a receiver or a combination of the above. In addition, the receivercan include other elements such as a DC to DC converter or regulatorsuch as a switching, buck, boost, buck/boost, or linear regulator. Thereceiver can also include a switch between the DC output of the receivercoil and the rectification and smoothing stage and its output or theoutput of the regulator stage to a device or battery or a device case orskin and in cases where the receiver is used to charge a battery ordevice, the receiver may also include a regulator, battery charger IC orcircuitry and/or battery protection circuit and associated transistors,etc. The receiver may also include variable or switchable reactivecomponents (capacitors and/or inductors) that would allow the receiverto change its resonant condition to affect the amount of power deliveredto the device, load or battery. The receiver and/or charger and/or theircoils can also include elements such as thermistors, magnetic shields ormagnetic cores, magnetic sensors, and input voltage filters, etc. forsafety and/or emission compliance reasons. The receiver may also becombined with other communication or storage functions such as NFC,WiFi, Bluetooth, etc. In addition, the charger and or receiver caninclude means to provide more precise alignment between the charger andreceiver coils or antennas. These can include visual, physical, ormagnetic means to assist the user in alignment of parts. To implementmore positioning freedom of the receiver on the charger, the size of thecoils can also be mismatched. For example, the charger can comprise alarger coil size and the receiver a smaller one or vice versa, so thatthe coils do not have to be precisely aligned for power transfer.

In simpler architectures, there may be minimal or no communicationbetween the charger and receiver. For example, a charger can be designedto be in a standby power transmitting state, and any receiver in closeproximity to it can receive power from the charger. The voltage, power,or current requirements of the device or battery connected to thereceiver circuit can be unregulated, or regulated or controlledcompletely at the receiver or by the device attached to it. In thisinstance, no regulation or communication between the charger andreceiver may be necessary. In a variation of this, the charger may bedesigned to be in a state where a receiver in close proximity wouldbring it into a state of power transmission. Examples of this would be aresonant system where inductive and/or capacitive components are used,so that when a receiver of appropriate design is in proximity to acharger, power is transmitted from the charger to a receiver; butwithout the presence of a receiver, minimal or no power is transmittedfrom the charger.

In a variation of the above, the charger can periodically be turned onto be driven with a periodic pattern (a ping process) and if a receiverin proximity begins to draw power from it, the charger can detect powerbeing drawn from it and would stay in a transmitting state. If no poweris drawn during the ping process, the charger can be turned off orplaced in a stand-by or hibernation mode to conserve power and turned onand off again periodically to continue seeking a receiver.

In accordance with an embodiment, the power section (coil drive circuitand receiver power section) can be a resonant converter, resonant, fullbridge, half bridge, E-class, zero voltage or current switching,flyback, or any other appropriate power supply topology. FIG. 2 shows amore detailed view of the wireless charger system 120 with a resonantconverter geometry, wherein a pair of transistors Q1 and Q2 (such asFETs, MOSFETs, or other types of switch) are driven by a half-bridgedriver IC and the voltage is applied to the coil L1 through one or morecapacitors shown as C1. The receiver includes a coil and an optionalcapacitor (for added efficiency) shown as C2 that may be in series or inparallel with the receiver coil L2. The charger and/or receiver coilsmay also include impedance matching circuits and/or appropriate magneticmaterial layers behind (on the side opposite to the coil surfaces facingeach other) them to increase their inductance and/or to shield themagnetic field leakage to surrounding area. The charger and/or receivermay also include impedance matching circuits to optimize/improve powertransfer between the charger and receiver.

In many of the embodiments and figures described herein, the resonantcapacitor C2 in the receiver is shown in a series architecture. This isintended only as a representative illustration, and this capacitor maybe used in series or parallel with the receiver coil. Similarly, thecharger is generally shown in an architecture where the resonantcapacitor is in series with the coil. System architectures with thecapacitor C1 is in parallel with the charger coil are also possible.

In accordance with an embodiment, the charger also includes a circuitthat measures the current through and/or voltage across the charger coil(in this case a current sensor is shown in the figure as an example).Various demodulation methods for detection of the communication signalon the charger current or voltage are available. This demodulationmechanism can be, for example, an AM or FM receiver (depending onwhether amplitude or frequency modulation is employed in the receivermodulator) similar to a radio receiver tuned to the frequency of thecommunication or a heterodyne detector, etc.

In accordance with an embodiment, the microcontroller unit (MCU) in thecharger (MCU1) is responsible for understanding the communication signalfrom the detection/demodulation circuit and, depending on the algorithmused, making appropriate adjustments to the charger coil drive circuitryto achieve the desired output voltage, current or power from thereceiver output. In addition, MCU1 is responsible for processes such asperiodic start of the charger to seek a receiver at the start of charge,keeping the charger on when a receiver is found and accepted as a validreceiver, continuing to apply power and making necessary adjustments,and/or monitoring temperature or other environmental factors, providingaudio or visual indications to the user on the status of charging orpower process, etc. or terminating charging or application of power dueto end of charge or customer preference or over temperature, overcurrent, over voltage, or some other fault condition or to launch orstart another program or process. For example, the charger can be builtinto a car, and when a valid receiver and/or an NFC, RFID or other IDmechanism integrated into or on a mobile device, its case or skin,dongle or battery is found, the charger may activate some otherfunctions such as Bluetooth connectivity to the device, displaying thedevice identity or its status or state of charge on a display, etc. Moreadvanced functions can also be activated or enabled by this action.Examples include using the device as an identification mechanism for theuser and setting the temperature of the car or the driver or passengerside to the user's optimum pre-programmed temperature, setting themirrors and seats to the preferred setting, starting a radio station ormusic preferred by user, etc., as described in U.S. Patent PublicationNo. 20110050164, incorporated by reference herein. The charger may alsoinclude an RF signal amplifier/repeater so that placement of a mobiledevice such as a mobile phone, tablet, etc. would provide close couplingand/or turning on of the amplifier and its antenna so that a bettersignal reception for communication such as cell phone calls can beobtained. Such Signal Boosters that include an antenna mounted on theoutside of a car, a bi-directional signal amplifier and a repeaterantenna inside a car are increasingly common. The actions launched orstarted by setting a device on a charger can also be different indifferent environments. Examples can include routing a mobile phone callor music or video from a smart phone to the speakers and microphones orvideo monitors or TV, computer, laptop, tablet, etc. in a car, home,office, etc. Other similar actions or different actions can be providedin other environments.

It may be useful in addition to the communication signal to detect theDC value of the current through the charger coil. For example, faultsmay be caused by insertion or presence of foreign objects such asmetallic materials between the charger and receiver. These materials maybe heated by the application of the power and can be detected throughdetection of the charger current or temperature or comparison of inputvoltage, current, or power to the charger and output voltage, current,or power from the receiver and concluding that the ratio is out ofnormal range and extra power loss due to unknown reasons is occurring.In these conditions or other situations such as abnormal charger and/orreceiver heating, the charger may be programmed to declare a faultcondition and shut down and/or alert the user or take other actions.

In accordance with an embodiment, once the charger MCU has received asignal and decoded it, it can take action to provide more or less powerto the charger coil. This can be accomplished through known methods ofadjusting the frequency, duty cycle or input voltage to the charger coilor a combination of these approaches. Depending on the system and thecircuit used, the MCU can directly adjust the bridge driver or anadditional circuit such as a frequency oscillator may be necessary todrive the bridge driver or the FETs.

A typical circuit for the receiver in accordance with an embodiment isalso shown in FIG. 2. In accordance with an embodiment, the receivercircuit can include a capacitor C2 in parallel or series with thereceiver coil to produce a tuned receiver circuit. This circuit is knownto increase the efficiency of a wireless power system. The rectified andsmoothed (through a bridge rectifier and capacitors) output of thereceiver coil and optional capacitor is either directly or through aswitch or regulator applied to the output. A microcontroller is used tomeasure various values such as output voltage, current, temperature,state of charge, battery full status, end of charge, etc. and to reportback to the charger to provide a closed loop system with the charger asdescribed above. In the circuit shown in FIG. 2, the receiver MCUcommunicates back to the charger by modulating the receiver load byrapidly closing and opening a switch in series with a modulation load ata pre-determined speed and coding pattern. This rapid load modulationtechnique at a frequency distinct from the power transfer frequency canbe easily detected by the charger. A capacitor and/or inductor can alsobe placed in parallel or in series with this load.

As an example, if one assumes that the maximum current output of thereceiver is 1000 mA and the output voltage is 5 V for a maximum outputof 5 W; in this case, the minimum load resistance is 5 ohms. Amodulation load resistor of several ohms (20, or 10 ohms or smaller)would be able to provide a large modulation depth signal on the receivercoil voltage. Choosing a 5 ohm resistor would modulate the outputbetween a maximum current of 1 Amp or larger and a smaller value definedby the device load at the output. Such a large modulation can be easilydetected at the charger coil current or voltage as described above.Other methods of communication through varying the reactive component ofthe impedance can also be used. The modulation scheme shown in FIG. 2 isshown only as a representative method and is not meant to be exhaustive.As an example, the modulation can be achieved capacitively, by replacingthe resistor with a capacitor. In this instance, the modulation by theswitch in the receiver provides the advantage that by choosing themodulation frequency appropriately, it is possible to achieve modulationand signal communication with the charger coil and circuitry, withminimal power loss (compared to the resistive load modulation).

The receiver in FIG. 2 also shows an optional DC regulator that is usedto provide constant stable voltage to the receiver MCU. This voltagesupply may be necessary to avoid drop out of the receiver MCU duringstartup conditions where the power is varying largely or during changesin output current and also to enable the MCU to have a stable voltagereference source so it can measure the output voltage accurately.Alternatively, a switch to connect or disconnect the load can be used orcombined with the regulator. To avoid voltage overshoots duringplacement of a receiver on a charger or rapid changes in load condition,a voltage limiter circuit or elements like Zener diodes or regulators orother voltage limiters can also be included in the receiver.

In the above description, a uni-directional communication (from thereceiver to the charger) is described. However, this communication canalso be bi-directional, and data can be transferred from the charger tothe receiver through modulation of the voltage or current in the chargercoil and read back by the microcontroller in the receiver detecting achange in the voltage or current, etc.

In accordance with other embodiments, and other geometries whereposition independence on placement of the receiver on the chargersurface is achieved by having multiple charger coils in an array orpattern, similar drive and communication circuits in the charger andreceiver can be implemented. To detect the appropriate coil to activatein the charger to achieve optimum power transfer to a receiver placed onthe charger, the charger coils can be activated in a raster or zigzagfashion or other geometry and current drawn from a charger coil,strength of voltage, current, power or signal from the receiver or othermethods can be used to determine the closest match between position ofone or more of the charger coils and a receiver coil and the appropriatecharger coil or coils can be activated and modulated to provide optimumpower transfer to the receiver.

While a system for communication between the charger and receiverthrough the power transfer coil or antenna is described above, inaccordance with an embodiment the communication can also be implementedthrough a separate coil, a radio frequency link (am or fm or othercommunication method), an optical communication system or a combinationof the above. The communication in any of these methods can also bebi-directional rather than uni-directional as described above. As anexample, FIG. 3 shows a system 130 in accordance with an embodiment,wherein a dedicated RF channel for uni-directional or bi-directionalcommunication between the charger and receiver is implemented forvalidation and/or regulation purposes. This system is similar to thesystem shown in FIG. 2, except rather than load modulation being themethod of communication, the MCU in the receiver transmits the necessaryinformation over an RF communication path. A similar system with LED orlaser transceivers or detectors and light sources can be implemented.Advantages of such system include that the power received is notmodulated and therefore not wasted during communication and/or that nonoise due to the modulation is added to the system.

One of the disadvantages of the circuit shown in FIG. 2 is that, in thereceiver circuit shown therein, the current path passes through 2 diodesand suffers 2 voltage drops resulting in large power dissipation andloss. For example, for Schottky diodes with forward voltage drop of 0.4V, at a current output of 1 A, each diode would lose 0.4 W of power fora combined power loss of 0.8 W for the two in a bridge rectifierconfiguration. For a 5 V, 1 A output power (5 W), this 0.8 W of powerloss presents a significant amount of loss (16%) just due to therectification system.

In accordance with an embodiment, an alternative is to use acenter-tapped receiver 140 as shown in FIG. 4, wherein during each cyclecurrent passes only through one part of the coil and one diode in thereceiver and therefore halves the rectification losses. Such a centertapped coil can be implemented in a wound-wire geometry with 2 sectionsof a wound wire or a printed circuit board coil or with a double ormulti-sided sided PCB coil or a combination or even a stamped, etched orotherwise manufactured coil or winding.

In any of the systems described above, as shown in FIG. 5, the chargerand receiver coils can be represented by their respective inductances150 by themselves (L1 and L2) and the mutual inductance between them Mwhich is dependent on the material between the two coils and theirposition with respect to each other in x, y, and z dimensions. Thecoupling coefficient between the coils k is given by:

k=M/(L1*L2)^(1/2)

The coupling coefficient is a measure of how closely the 2 coils arecoupled and may range from 0 (no coupling) to 1 (very tight coupling).In coils with small overlap, large gap between coils or dissimilar coils(in size, number of turns, coil winding or pattern overlap, etc.), thisvalue can be smaller than 1.

FIG. 6 shows a wirelessly powered battery pack and receiver 160 inaccordance with an embodiment. The components of a typical commonbattery pack (battery cell and protection circuit, etc.) used in abattery device used in applications such as mobile phone, etc. are showninside the dashed lines. The components outside the dashed lines areadditional components that are included to enable safe wireless andwired charging of a battery pack. A battery pack may have four or moreexternal connector points that interface with a mobile device pins in abattery housing or with an external typical wired charger. In accordancewith an embodiment 170, the battery cell is connected as shown in FIG. 7to two of these connectors (shown in the figure as BATT+ and BATT−)through a protection circuit comprising a battery protection IC thatprotects a battery from over-current and under or over voltage. Atypical IC can be Seiko 8241 IC that uses 2 external Field EffectTransistors (FETs) as shown in FIG. 7 to prevent current going from orto the battery cell (on the left) from the external battery packconnectors if a fault condition based on over current, or battery cellover or under voltage is detected. This provides safety during chargingor discharging of the battery. In addition, a battery pack can include aPTC conductive polymer passive fuse. These devices can sense and shutoff current by heating a layer inside the PTC if the amount of currentpassing exceeds a threshold. The PTC device is reset once this currentfalls and the device cools.

In addition, in accordance with an embodiment, the battery pack cancontain a thermistor, which the mobile device checks through one otherconnector on the battery pack to monitor the health of the pack, and insome embodiments an ID chip or microcontroller that the mobile deviceinterrogates through another connector to confirm an original batterymanufacturer or other information about the battery. Other connectorsand functions can be included in a battery pack to provide accuratebattery status and/or charging information to a device being powered bya battery pack or a charger charging the battery pack.

In addition to the components described above, in accordance with anembodiment, the receiver circuit comprises a receiver coil that can be awound wire and/or PCB coil as described above, optional electromagneticshielding between the coil and the metal body of the battery, optionalalignment assisting parts such as magnets, etc., a receivercommunication circuit (such as the resistor and FET for load modulationshown in FIG. 2 and FIG. 4), a wireless power receiver (such asrectifiers and capacitors as described above), and an optional Batterycharger IC that has a pre-programmed battery charging algorithm. Eachtype of battery and chemistry requires a pre-determined optimizedprofile for charging of that battery type. A typical charge cycle 180for a Lithium Ion (Li-Ion) is shown in FIG. 8. Such a battery can becharged up to a value of 4.2 V at full capacity. The battery should becharged according to the guidelines of the manufacturer. For a batteryof capacity C, the cell can typically be charged at the rate 1C. InStage 1, the maximum available current is applied and the cell voltageincreases until the cell voltage reaches the final value (4.2 V). Inthat case, the charger IC switches to Stage 2 where the charger ICswitches to Constant Voltage charging where the cell voltage does notchange but current is drawn from the source to further fill up thebattery. This second Stage may take 1 or more hours and is necessary tofully charge the battery. Eventually, the battery will draw little(below a threshold) or no current. At this stage, the battery is fulland the charger may discontinue charging. The charger IC canperiodically seek the condition of the battery and top it off further ifthe battery has drained due to stand-by, etc.

In accordance with an embodiment, such multiple stages of batterycharging can be implemented in firmware with the wireless power chargerand receiver microcontrollers monitoring the battery cell voltage,current, etc. and working in tandem and to provide appropriate voltage,current, etc. for safe charging for any type of battery. In anotherapproach as shown in FIG. 6, a battery charger IC chip that hasspecialized battery charging circuitry and algorithm for a particulartype of battery can be employed. These charger ICs (with or without fuelgauge capability to accurately measure battery status, etc.) areavailable for different battery chemistries and are included in mostmobile devices with mobile batteries such as mobile phones. They caninclude such safety features as a temperature sensor, open circuit shutoff, etc. and can provide other circuits or microcontrollers such usefulinformation as end of charge signal, signaling for being in constantcurrent or voltage (stage 1 or 2 above, etc.). In addition, some ofthese ICs allow the user to program and set the maximum output currentto the battery cell with an external resistor across 2 pins of the IC.

In accordance with an embodiment, the wirelessly charged battery pack inaddition includes a micro-controller that coordinates and monitorsvarious points and may also include thermal sensors on the wirelesspower coil, battery cell and/or other points in the battery pack. Themicrocontroller also may communicate to the charger and can also monitorcommunication from the charger (in case of bi-directionalcommunication). Typical communication through load modulation isdescribed above.

In accordance with an embodiment, another aspect of a wirelessly chargedbattery pack can be an optional external/internal switch. A battery packcan receive power and be charged wirelessly or through the connectors ofa battery pack. For example, when such a battery pack is used in amobile phone, the user may wish to place the phone on a wireless chargeror plug the device in to a wired charger for charging or charge thedevice as well as synchronize or upload and/or download data or otherinformation. In the second case, it may be important for the batterypack to recognize current incoming to the battery pack and to take somesort of action. This action can include, e.g. notifying the user,shutting off the wired charger by a switch or simply shutting down thecharger IC and sending a signal back through the microcontroller andmodulating the current back to the charger that a wired charger ispresent (in case priority is to be given to the wired charger) orconversely to provide priority to the wireless charger and shut offwired charger access to battery when the wireless charger is chargingthe battery. At either case, a protocol for dealing with presence of twochargers simultaneously should be pre-established and implemented inhardware and firmware.

As shown in FIG. 6, the wireless charging of battery occurs with currentflowing into the battery through the battery contacts from the mobiledevice. Typically, such current is provided by an external DC supply tothe mobile device (such as an AC/DC adaptor for a mobile phone) and theactual charging is handled by a charger IC chip or power management ICinside the mobile device that in addition to charging the battery,measures the battery's state of charge, health, verifies batteryauthenticity, and displays charge status through LEDs, display, etc. toa user. It may therefore be advantageous to include a current sensecircuit at one of the battery pack contacts to measure and sense thedirection of current flow into or out of the battery. In situationswhere the current is flowing inwards (i.e. the battery is beingexternally charged through a wired charging connection, and/or through amobile device), the micro-controller can take the actions describedabove and shut off wireless charging or conversely, provide priority towireless charging and if it is present, allow or disallow wired chargingas the implementation requires.

In many applications, it is important to include a feature that caninform a mobile device user about the state of charge of a battery packin the device. To enable an accurate measurement of the remainingbattery charge, several gas gauging techniques can be implemented, ingeneral by incorporating a remaining charge IC or circuitry in thebattery or in the device. In accordance with an embodiment, the mobiledevice can also include a Power Management Integrated Circuit (PMIC) ora fuel or battery gauge that communicates with the wirelessly chargeablebattery and measures its degree of charge and display this status on themobile device display or inform the user in other ways. In anotherembodiment, this information is transmitted to the charger and alsodisplayed on the charger. In typical circumstances, a typical fuel gaugeor PMIC may use battery voltage/impedance, etc. as well as measurementof the current and time for the current entering the mobile device(coulomb counting) to determine the status of the battery charge.However in a wirelessly charged system, this coulomb counting may haveto be carried out in the battery rather than in the mobile device, andthen communicated to the mobile device or the charger, since the chargeis entering the battery directly through the onboard wireless powerreceiver and circuitry. The communication between the mobile device andthe battery is through the connectors of the battery and may involvecommunication with an on-board microcontroller in the battery pack. Inaccordance with an embodiment, the wirelessly chargeable battery packcan include appropriate microcontroller and/or circuitry to communicatewith the mobile device or wireless charger circuitry and update itsstate of charge, even though no current may be externally applied(through a wired power supply or charger) to the mobile device and thebattery is charged wirelessly. In simpler fuel gauge techniques, thebattery voltage, impedance, etc. can be used to determine battery chargestatus, and that in turn can be accomplished by performing appropriatemeasurements by the mobile device circuitry through battery connectorpoints or by appropriate circuitry that may be incorporated in thewirelessly chargeable battery pack and/or in the mobile device or itsPMIC or circuitry. FIG. 6 shows an embodiment where a microcontroller orcircuit inside the battery pack is included to accomplish the fuel gaugetask and report the state of charge to the device. This circuitry can bethe same, or different, from an ID chip used to identify the battery andcan communicate through a common battery connector or a separate one.

In accordance with an embodiment, the firmware in the receivermicro-controller plays a key role in the operation of this battery pack.The micro-controller can measure voltages and currents, flags, andtemperatures at appropriate locations for proper operation. Inaccordance with one embodiment, by way of example, the micro-controllercan measure the value of V_(out) from the rectifier circuit and attemptto keep this constant throughout the charging cycle thereby providing astable regulated DC supply to the charger IC chip. The microcontrollercan report the value of this voltage or error from a desired voltage(for example 5V) or simply a code for more or less power back to thecharger in a binary or multi-level coding scheme through a loadmodulation or other scheme (for example RF communication, NFC,Bluetooth, etc. as described earlier) back to the charger. The chargercan then take action through adjustment of input voltage to the chargercoil, adjustment of the frequency or duty cycle of the AC voltageapplied to the charger coil to bring the V_(out) to within requiredvoltage range or a combination of these actions or similar methods. Themicro-controller throughout the charging process, in addition, maymonitor the end of charge and/or other signals from charger and/orprotection circuit and the current sense circuit (used to sense batterypack current direction and value) to take appropriate action. Li-Ionbatteries for example need to be charged below a certain temperature forsafety reasons. In accordance with an embodiment, it is thereforedesirable to monitor the cell, wireless power receiver coil or othertemperature and to take appropriate action, such as to terminatecharging or lower charging current, etc. if a certain maximumtemperature is exceeded.

It will be noted that during charging, as shown in FIG. 8, the batterycell voltage increases from 3 V or lower, to 4.2 V, as it is charged.The V_(out) of the wireless power receiver is input to a charger IC andif this V_(out) is kept constant (for example 5V), a large voltage drop(up to 2 V or more) can occur across this IC especially during Stage 1where maximum current is applied. With charging currents of up to 1 A,this may translate to up to 2 Watts of wasted power/heat across this ICthat may contribute to battery heating. In accordance with anembodiment, it is therefore desirable to implement a strategy wherebythe V_(out) into the charger IC tracks the battery voltage therebycreating a smaller voltage drop and therefore loss across the chargerIC. This can provide a significant improvement in performance, sincethermal performance of the battery pack is very important.

In accordance with an embodiment, the communication between the receiverand charger needs to follow a pre-determined protocol, baud rate,modulation depth, etc. and a pre-determined method for hand-shake,establishment of communication, and signaling, etc. as well asoptionally methods for providing closed loop control and regulation ofpower, voltage, etc. in the receiver.

In accordance with an embodiment, a typical wireless power systemoperation 190 as further shown in FIG. 9 can be as follows: the chargerperiodically activates the charger coil driver and powers the chargercoil with a drive signal of appropriate frequency. During this ‘ping’process, if a receiver coil is placed on top or close to the chargercoil, power is received through the receiver coil and the receivercircuit is energized. The receiver microcontroller is activated by thereceived power and begins to perform an initiation process whereby thereceiver ID, its presence, power or voltage requirements, receiver orbattery temperature or state of charge and/or other information is sentback to the charger. If this information is verified and found to bevalid, then the charger proceeds to provide continuous power to thereceiver. The receiver can alternately send an end of charge,over-temperature, battery full, or other messages that will be handledappropriately by the charger and actions performed. The length of theping process should be configured to be of sufficient length for thereceiver to power up its microcontroller and to respond back and for theresponse to be received and understood. The length of time between thepings can be determined by the implementation designer. If the pingprocess is performed often, the stand-by power use of the charger ishigher. Alternately, if the ping is performed infrequently, the systemwill have a delay before the charger discovers a receiver nearby. So inpractice, a balance must be achieved.

Alternately, the ping operation can be initiated upon discovery of anearby receiver by other means. This provides a very low stand-by poweruse by the charger and may be performed by including a magnet in thereceiver and a magnet sensor in the charger or through optical,capacitive, weight, NFC or Bluetooth, RFID or other RF communication orother methods for detection. Alternatively, the system can be designedor implemented to be always ON (i.e. the charger coil is powered at anappropriate drive frequency) or pinged periodically and presence of thereceiver coil brings the coil to resonance with the receiver coil andpower transfer occurs. The receiver in this case may not even contain amicrocontroller and act autonomously and may simply have a regulator inthe receiver to provide regulated output power to a device, its skin,case, or battery. In those embodiments in which periodic pinging isperformed, the presence of a receiver can be detected by measuring ahigher degree of current flow or power transfer or other means and thecharger can simply be kept on to continue transfer of power until eitherthe power drawn falls below a certain level or an end of charge and/orno device present is detected. In another embodiment, the charger may bein an off or standby, or low or no power condition, until a receiver isdetected by means of its presence through a magnetic, RF, optical,capacitive or other methods. For example, in accordance with anembodiment the receiver can contain an RFID chip and once it is presenton or nearby the charge, the charger would turn on or begin pinging todetect a receiver.

In accordance with an embodiment, the protocol used for communicationcan be any of, e.g. common RZ, NRZ, Manchester code, etc. used forcommunication. An example of the communication process and regulation ofpower and/or other functions is shown in FIG. 10. As described above,the charger can periodically start and apply a ping voltage 200 ofpre-determined frequency and length to the charger coil (as shown in thelower illustration in FIG. 10). The receiver is then activated, and maybegin to send back communication signals as shown in top of FIG. 10. Thecommunication signal can include an optional preamble that is used tosynchronize the detection circuit in the charger and prepare it fordetection of communication. A communication containing a data packet maythen follow, optionally followed by checksum and parity bits, etc.Similar processes are used in communication systems and similartechniques can be followed. In accordance with an embodiment, the actualdata packet can include information such as an ID code for the receiver,received voltage, power, or current values, status of the battery,amount of power in the battery, battery or circuit temperature, end ofcharge or battery full signals, presence of external wired charger, or anumber of the above. Also this packet may include the actual voltage,power, current, etc. value or the difference between the actual valueand the desired value or some encoded value that will be useful for thecharger to determine how best to regulate the output.

Alternatively, the communication signal can be a pre-determined patternthat is repetitive and simply lets the charger know that a receiver ispresent and/or that the receiver is a valid device within the powerrange of the charger, etc. Any combination of systems can be designed toprovide the required performance.

In response to the receiver providing information regarding output poweror voltage, etc. the charger can modify voltage, frequency, duty cycleof the charger coil signal or a combination of the above. The chargercan also use other techniques to modify the power out of the chargercoil and to adjust the received power. Alternatively the charger cansimply continue to provide power to the receiver if an approved receiveris detected and continues to be present. The charger may also monitorthe current into the charger coil and/or its temperature to ensure thatno extra-ordinary fault conditions exist. One example of this type offault may be if instead of a receiver, a metal object is placed on thecharger.

In accordance with an embodiment, the charger can adjust one or moreparameters to increase or decrease the power or voltage in the receiver,and then wait for the receiver to provide further information beforechanging a parameter again, or it can use more sophisticatedProportional Integral Derivative (PID) or other control mechanism forclosing the loop with the receiver and achieving output power control.Alternatively, as described above, the charger can provide a constantoutput power, and the receiver can regulate the power through aregulator or a charger IC or a combination of these to provide therequired power to a device or battery.

Various manufacturers may use different encodings, and also bit ratesand protocols. The control process used by different manufacturers mayalso differ, further causing interoperability problems between variouschargers and receivers. A source of interoperability differences may bethe size, shape, and number of turns used for the power transfer coils.Furthermore, depending on the input voltage used, the design of awireless power system may step up or down the voltage in the receiverdepending on the voltage required by a device by having appropriatenumber of turns in the charger and receiver coils. However, a receiverfrom one manufacturer may then not be able to operate on anothermanufacturer charger due to these differences in designs employed. It istherefore beneficial to provide a system that can operate with differentreceivers or chargers and can be universal.

The resonant frequency, F of any LC circuit is given by:

F=1/(2π√{square root over (LC)})

Where L is the Inductance of the circuit or coil in Henry and C is theCapacitance in Farads. For the system shown in FIG. 2, one may use thevalues of C1 and L1 in the above calculation for a free running chargerand as a Receiver is brought close to this circuit, this value ischanged by the mutual coupling of the coils involved. It must be notedthat in case a ferrite shield layer is used behind a coil in the chargerand/or receiver, the inductance of the coil is affected by thepermeability of the shield and this modified permeability should be usedin the above calculation. In accordance with an embodiment, to be ableto detect and power/charge various receivers, the charger can bedesigned such that the initial ping signal is at such a frequency rangeto initially be able to power and activate the receiver circuitry in anyreceiver during the ping process. After this initial power up of thereceiver, the charger communication circuit should be able to detect andunderstand the communication signal from the receiver. Manymicrocontrollers are able to communicate in multiple formats and mayhave different input pins that can be configured differently tosimultaneously receive the communication signal and synchronize andunderstand the communication at different baud rates and protocols. Inaccordance with an embodiment, the charger firmware can then decide onwhich type of receiver is present and proceed to regulate or implementwhat is required (end of charge, shut-off, fault condition, etc.).Depending on the message received, the charger can then decide to changethe charger driver voltage amplitude, frequency, or duty cycle, or acombination of these or other parameters to provide the appropriateregulated output.

In accordance with an embodiment, the charger's behavior can also takeinto account the difference in the coil geometry, turns ratio, etc. Forexample, a charger and receiver pair from one or more manufacturers mayrequire operation of the charger drive voltage at 150 kHz. However, ifthe same receiver is placed on a charger from another manufacturer ordriven with different coil/input voltage combination, to achieve thesame output power, the charger frequency may need to be 200 kHz. Thecharger program may detect the type of receiver placed on it and shiftthe frequency appropriately to achieve a baseline output power andcontinue regulating from there. In accordance with an embodiment, thecharger can be implemented so that it is able to decode and implementmultiple communication and regulation protocols and respond to themappropriately. This enables the charger to be provided as part of amulti-protocol system, and to operate with different types of receivers,technologies and manufacturers.

For receivers that contain an onboard regulator for the output power,stability of the input voltage to the regulator is not as critical sincethe regulator performs a smoothing function and keeps the output voltageat the desired level with any load changes. It is however, important notto exceed the maximum rated input voltage of the regulator or to dropbelow a level required so that the output voltage could no longer bemaintained at the required value. However, in general, inclusion of aregulator and/or a charger IC chip (for batteries) reduces thepower/voltage regulation requirements of the wireless power receiverportion of the circuit at the expense of the additional size and cost ofthis component. In accordance with some embodiments, simpler voltagelimiting output stages such as Zener diodes or other voltage limiting orclamping ICs or circuits, can be used.

While the system above describes a system wherein the communication isprimarily through the coil, as described earlier, communication can alsobe implemented through a separate coil, RF, optical system or acombination of the above. In such circumstances, a multi-protocol systemcan also be used to interoperate between systems with differentcommunication and/or control protocols or even means of communication.

Electromagnetic Interference (EMI) is an important aspect of performanceof any electronic device. Any device to be sold commercially requiresadherence to regulation in different countries or regions in terms ofradiated power from it. Any power supply (wired or wireless) thatincludes high frequency switching can produce both conducted andradiated electromagnetic interference (EMI) at levels that exceed theacceptable limits so extreme care must be taken to keep such emissionsto a minimum.

For an inductive charger comprising a number of coils and electronicsswitches and control circuitry, the main sources of emission include:

Any potential radiated noise from switching FETS, drivers, etc. or senseand control circuitry. This noise can be at higher frequency than thefundamental drive frequency of the coils and can be emitted away fromthe charger because of the frequency. This noise can be minimized byoptimizing the drive circuit to avoid sharp edges in the drive waveformand associated noise.

Noise from copper traces with AC signals. This noise can also be athigher frequency and emit away from the charger. The length of thesepaths must be minimized.

EM emission from the switched coil. For coils described here and drivenin the 100's of kHz up to several MHz, the wavelength of theElectromagnetic (EM) field generated can be in the hundreds of meters.Given the small length of the coils windings (often 1 m or less), thecoils used are not efficient far-field transmitters of the EM field andthe generated EM field is in general highly contained near the coilsurface. The magnetic flux pattern from a PCB coil is highly containedin the area of a coil and does not emit efficiently away from the coil.

Care must be taken when designing the current paths, and in someembodiments shielding of the FETs or other ICs or electronics componentsmay be necessary. In addition, switching the coils with waveforms thathave higher frequency components, gives rise to noise at higherfrequencies. In any of the above geometries described, incorporation ofconductive layers and/or ferromagnetic layers in the system can shieldthe outside environment from any potential radiative fields. Theconductive layers may be incorporated in the PCB to eliminate the needfor additional separate shielding layers.

In any of the configurations described here, care must be taken whendesigning the current paths, and in some embodiments shielding of theFETs or other ICs or electronics components may be necessary. Theshielding may be implemented by incorporation of ferrite or metal sheetsor components or a combination thereof. Use of thin layers (typicallyseveral micrometers of less in thickness) of metal or other conductivepaint, polymer, nano material, dielectric or alike that take advantageof frequency dependence of the skin effect to provide a frequencydependent shielding or attenuation have been described in other patentapplications (for example, U.S. Patent Publication No. 2009/0096413,herein incorporated by reference) where a process for incorporating athin layer of metal in the top layer or other areas of the charger havebeen described. Since the layer does not absorb incident EM fields atthe frequency of operation of the device, they would pass through evenon the top surface of the charger (facing the charger coil) but higherfrequency components would be absorbed reducing or eliminating theharmful effect of higher frequency components radiation to nearbydevices, interference, or effects on living organisms or humans andmeeting regulatory conditions for operation. It is therefore possible toincorporate the charger or receiver into parts or products where thecharger and/or receiver coil is covered by a thin layer of conductive orconductive containing material or layer. Such conductive material mayinclude metallic, magnetic, plastic electronic or other material orlayers.

In many situations the frequency content of any EMI emissions from thewireless charger and receiver is important, and care must be taken thatthe fundamental frequency and its harmonics do not exceed requiredvalues and do not cause unnecessary interference with other electronicdevices, vehicles or components nearby. In accordance with anembodiment, one method that can be used to reduce the peak value of suchemissions is to intentionally introduce a controlled dither (variation)to the frequency of the operation of the charger. Such a dither wouldreduce the peak and spread the frequency content of the fundamentalemission and its harmonic over a range of frequencies determined by theamount of the dither or shift introduced. Appropriate implementation ofdither can reduce undesired interference issues at a given frequency toacceptable levels. However, the overall emitted power may not bereduced. To introduce a dither in any of the systems described here, thecharger driver can be appropriately driven by the MCU to dither itsoperating frequency or this can be hard wired into the design.Introduction of dither would typically introduce a slow ripple to theoutput voltage from the receiver. However, this slow ripple can be keptto a minimum or a regulator or circuit can be incorporated into thereceiver to reduce this ripple to an acceptable level or to eliminateit.

In accordance with an embodiment, the multi-protocol approachesdescribed here are important for development of a universal system thatcan operate amongst multiple systems and provide user convenience.

In accordance with an embodiment, the systems described here may usediscreet electronics components or some or all of the functionsdescribed above may be integrated into an Application SpecificIntegrated Circuit (ASIC) to achieve smaller footprint, betterperformance/noise, etc. and/or cost advantages. Such integration iscommon in the Electronics industry and can provide additional advantageshere.

In many cases, for the systems described above, the transmitter andreceiver coils may be of similar, although not necessarily same sizesand are generally aligned laterally to be able to transfer powerefficiently. For coils of similar size, this would typically require theuser to place the device and/or receiver close to alignment with respectto the transmitter coil. For example, for a transmitter/receiver coil of30 mm diameter, this would require lateral (x,y) positioning within 30mm so there is some degree of overlap between the coils. In practice, aconsiderable degree of overlap is necessary to achieve high outputpowers and efficiencies. This may be achieved by providing mechanical orother mechanisms such as indentations, protrusions, walls, holders,fasteners, etc. to align the parts.

However, for a universal charger/power supply to be useful for chargingor powering a range of devices, a design able to accept any device andreceiver is desirable. For this reason, in accordance with anembodiment, a flat or somewhat curved charger/power supply surface thatcan be used with any type of receiver may be used. To achieve alignmentin this case, markings, small protrusions or indentations and/or audioand/or visual aids or similar methods can be used. Another methodincludes using magnets, or magnet(s) and magnetic or ferrite magneticattractor material(s) that can be attracted to a magnet in thetransmitter/charger and receiver. In these methods, typically a singlecharger/transmitter and receiver are in close proximity and aligned toeach other.

However, for even greater ease of use, it may be desirable to be able toplace the device to be charged/powered over a larger area, withoutrequiring precise alignment of coils. There are several methods thathave been previously used for this.

Several other methods that address the topic of position independencehave been described previously. For example, as described in U.S. PatentPublication No. 20070182367 and U.S. Patent Publication No. 20090096413,both of which applications are herein incorporated by reference, anembodiment comprising multiple transmitter coils arranged in atwo-dimensional array to cover and fill the transmitter surface isdescribed. When a receiver is placed on the surface of such a coilarray, the transmitter coil with the largest degree of overlap with thereceiver is detected and activated to allow optimum power transmissionand position independent operation. The detection mechanism can bethrough, e.g. detection of weight, capacitive, optical, mechanical,magnetic RFID, RF, or electrical sensing of the receiver. In accordancewith an embodiment, the coils in the charger/power supply aresequentially powered (pinged) and the charger/power supply waits for anypossibly receivers to be powered up and reply to the ping. If no replyis detected back within a time window, the next coil is activated, etc.until a reply is detected in which case the charger/power supplyinitiates power up of the appropriate transmitter coil(s) and proceedsto charge/power the receiver.

In another geometry, each transmitter (or charger) coil center includesa sensor inductor (for example, E. Waffenschmidt, and Toine Staring,13th European Conference on Power Electronics and Applications,Barcelona, 2009. EPE '09. pp. 1-10). The receiver coil includes a softmagnetic shield material that shifts the resonance frequency response ofthe system and can be sensed by a sensor in the transmitter to switchthe appropriate coil on. The drawback of this system is that 3 layers ofoverlapping coils with a sensor and detection circuit at the center ofeach is required adding to the complexity and cost of the system. Othervariations of the above or a combination of techniques can be used todetect the appropriate transmitter coil.

In accordance with other embodiments, described in U.S. PatentPublication No. 2007/0182367 and U.S. Patent Publication No.2009/0096413, the charger/power supply may contain one or moretransmitter coils that are suspended and free to move laterally in thex-y plane behind the top surface of the charger/power supply. When areceiver coil is placed on the charger/power supply, the closesttransmitter coil would move laterally to position itself to be under andaligned with the receiver coil. One passive method of achieving this maybe to use magnets or a combination of magnet(s) and attractor(s) (one ormore attached to the transmitter coil or the movable charging componentand one or more to the receiver coil or receiver) that would attract andpassively align the two coils appropriately. In another embodiment, asystem that detects the position of the receiver coil on thecharger/power supply surface and uses this information to move thetransmitter coil to the appropriate location actively using motors,piezo or other actuators, etc. is possible.

In general, the systems above describe use coils that are of similarsize/shape and in relatively close proximity to create a wireless powersystem.

As described above, the coupling coefficient k is an important factor indesign of the wireless power system. In general, wireless power systemscan be categorized into two types. One category which is called tightlycoupled operates in a parameter space where the k value is typically 0.5or larger. This type of system is characterized by coils that aretypically similar in size and/or spatially close together in distance (zaxis) and with good lateral (x,y) overlap. This so called tightlycoupled system is typically associated with high power transferefficiencies defined here as the ratio of output power from the receivercoil to input power to transmitter coil. The methods described above forposition independent operation (array of transmitter coils and movingcoils), typically may use tightly coupled coils.

In contrast, for coils of dissimilar size or design or largertransmitter to receiver distance or smaller lateral coil overlap, thesystem coupling coefficient is lower. Another important parameter, thequality factor of a transmitter (tx) and receiver (rx) coil is definedas:

Q _(tx)=2πf L _(tx) /R _(tx)

Q _(rx)=2πf L _(rx) /R _(rx)

where f is the frequency of operation, L_(tx) and L_(rx) the inductancesof the transmitter and receiver coils and R_(tx) and R_(rx) theirrespective resistances. The system quality factor can be calculated asfollows:

Q=(Q _(tx) Q _(rx))^(1/2)

In general, the loosely coupled systems may have smaller power transferefficiencies. However, it can be shown (see for example, E.Waffenschmidt, and Toine Staring, 13th European Conference on PowerElectronics and Applications, Barcelona, 2009. EPE '09. pp. 1-10) thatan increase of Q can compensate for smaller k values, and reasonable orsimilar power transfer efficiencies can be obtained. Such systems withdissimilar coil sizes and higher Q values are sometimes referred to asResonant Coupled or Resonant systems. However, resonance is also oftenused in the case of similar-size coil systems. Others, (such as AndréKurs, Aristeidis Karalis, Robert Moffatt, J. D. Joannopoulos, PeterFisher, and Marin Soljac, Science, 317, P. 83-86, 2007; andhttp://newsroom.intel.com/docs/DOC-1119) have shown that with systemswith k of <0.2 due to large distance between coils (up to 225 cm),sizeable reported power transfer efficiencies of 40%-70% can beobtained. Other types of loosely coupled system appear to usemis-matched coils where the transmitter coil is much larger than thereceiver coil (see for example, J. J. Casanova, Z. N. Low, J. Lin, andRyan Tseng, in Proceedings of Radio Wireless Symposium, 2009, pp.530-533 and J. J. Casanova, Z. N. Low, and J. Lin, IEEE Transactions onCircuits and Systems—II: Express Briefs, Vol. 56, No. 11, November 2009,pp. 830-834 and a Fujitsu System described athttp://www.fujitsu.com/global/news/pr/archives/month/2010/20100913-02.html).

Previous references (e.g., U.S. Pat. Nos. 6,906,495, 7,239,110,7,248,017, and 7,042,196) describe a loosely coupled system for chargingmultiple devices whereby a magnetic field parallel to the plane of thecharger is used. In this case, the receiver contains a coil that istypically wrapped around a magnetic material such as a rectangular thinsheet and has an axis parallel to the plane of the charger. To allow thecharger to operate with the receiver rotated to any angle, two sets ofcoils creating magnetic fields parallel to the plane of the charger at90 degrees to each other and driven out of phase are used.

Such systems may have a larger transmitter coil and a smaller receivercoil and operate with a small k value (possibly between 0 and 0.5depending on coil size mismatch and gap between coils/offset of coils).Of course the opposite case of a small transmitter coil and largerreceiver coil is also possible.

FIG. 11 shows configurations 220 for a tightly coupled power transfersystem with 2 individual transmitter coils of different size powering alaptop and a phone (left) and a loosely coupled wireless power systemwith a large transmitter coil powering 2 smaller receiver coils inmobile phones (right).

An ideal system with largely mis-matched (i.e. dissimilar in size/shape)coils can potentially have several advantages:

(1) Power can be transferred to the receiver coil placed anywhere on thetransmitter coil.

(2) Several receivers can be placed and powered on one transmitterallowing for simpler and lower cost of transmitter.

(3) The system with higher Q can be designed so the gap between thetransmitter and receiver coil can be larger than a tightly coupledsystem leading to design of systems with more design freedom. Inpractice, power transfer in distances of several cm or even higher havebeen demonstrated.

(4) Power can be transferred to multiple receivers simultaneously. Inaddition, the receivers can potentially be of differing power rating orbe in different stages of charging or require different power levelsand/or voltages.

In order to achieve the above characteristics and to achieve high powertransfer efficiency, the lower k value is compensated by using a higherQ through design of lower resistance coils, etc. The power transfercharacteristics of these systems may differ from tightly coupled systemsand other power drive geometries such as class E amplifier or ZeroVoltage Switching (ZVS) or Zero Current Switching (ZCS) or other powertransfer systems may operate more efficiently in these situations. Inadditions, impedance matching circuits at the charger/transmitter and/orreceiver may be required to enable these systems to provide power over arange of load values and output current conditions. General operation ofthe systems can, however be quite similar to the tightly coupled systemsand one or more capacitors in series or parallel with the transmitterand/or receiver coil is used to create a tuned circuit that may have aresonance for power transfer. Operating near this resonance point,efficient power transfer across from the transmitter to the receivercoil can be achieved. Depending on the size difference between the coilsand operating points, efficiencies of over 50% up to near 80% have beenreported.

To provide more uniform power transfer across a coil, methods to providea more uniform magnetic field across a coil can be used. One method forachieving this uses a hybrid coil comprising a combination of a wire andPCB coils (see, for example, X. Liu and S. Y. R. Hui, “Optimal design ofa hybrid winding structure for planar contactless battery chargingplatform,” IEEE Transactions on Power Electronics, vol. 23, no. 1, pp.455-463, 2008). In another method, the transmitter coil is constructedof Litz wire and has a pattern that is very wide between successiveturns at the center and is more tightly wound as one gets closer to theedges (see, for example, J. J. Casanova, Z. N. Low, J. Lin, and R.Tseng, “Transmitting coil achieving uniform magnetic field distributionfor planar wireless power transfer system,” in Proceedings of the IEEERadio and Wireless Symposium, pp. 530-533, January 2009). FIG. 12 showsa coil 230 demonstrated therein, while FIG. 13 shows the resultingcalculated magnetic field 240. In a geometry described in U.S. PatentPublication No. 2008/0067874, also incorporated herein by reference, aplanar spiral inductor coil is demonstrated, wherein the width of theinductor's trace becomes wider as the trace spirals toward the center ofthe coil to achieve a more uniform magnetic field allowing morepositioning flexibility for a receiver across a transmitter surface. Inyet other embodiments (F. Sato, et al., IEEE Digest of Intermag 1999,PP. GR09, 1999), the coil can be a meandering type of coil wherein thewire is stretched along X direction and then folds back and makes a backand forth pattern to cover the surface.

In accordance with an embodiment, the charger can operate continuously,and any receiver placed on or near its surface will bring it toresonance and will begin receiving power. The regulation of power to theoutput can be performed through a regulation stage at the receiver.Advantages of such a system include that multiple receivers withdifferent power needs can be simultaneously powered in this way. Thereceivers may also have different output voltage characteristics. Toachieve this, the number of turns on the receiver coil can be changed toachieve different receiver output voltages. Without any receiversnearby, such a charger would not be in resonance and would draw minimalpower. At end of charge, the receiver can include a switch that willdetect the minimal current draw by a device connected to the receiver,and disconnect the output altogether and/or disconnect the receiver coilso that the receiver is no longer drawing power. This will bring thecharger out of resonance and minimal input current is drawn at thisstage.

In accordance with another embodiment, the charger can periodically pingfor receivers, and initiate and maintain power transfer if sufficientcurrent draw from a receiver is detected. Otherwise, the charger canreturn to standby and continue pinging. Such a system would have evenlower stand-by power usage.

In a more complex system, similar communication and control and/orreceiver detection as described for the tightly coupled situationearlier can be applied for such loosely coupled systems. However, awireless power system designed to power multiple receivers placed on asingle transmitter (see, for example, “Qualcomm Universal Charging”available athttp://www.qualcomm.com/common/documents/articles/eZone_052609.pdf) mayneed to regulate the power transfer and the voltage at each receiverdifferently depending on the status of the load/device that the power isbeing delivered to. In cases where multiple receivers are placed on onetransmitter coil and it is desired to power/charge all devices, allreceivers may try to communicate with the transmitter and thetransmitter will need to distinguish between receivers and operatedifferently (e.g. at different power level, or switching frequency,etc.) with each one. Since the transmitter coil emits power to all thereceivers, it may be difficult to regulate power delivered to eachreceiver differently. Therefore in a practical system, some degree ofregulation of power to be delivered to a load or device may be performedin the receiver circuitry.

In another method of regulation, each receiver may time-share thetransmitter power. Each receiver placed on a transmitter may synchronizeand communicate with the transmitter and/or with other receivers throughwireless RF communication or RFID or Near Field Communication,Bluetooth, WiFi, or communication through power transfer and/or separatecoils or through optical or other methods. The transmitter may thenpower each receiver sequentially and deliver the appropriate power levelthrough adjustment of the transmitter frequency, pulse width modulation,or adjustment of input voltage, or a combination of above methods. Inorder for this system to operate, it may be necessary for all or some ofthe receivers to disconnect from receipt of power during the time periodwhen one receiver is receiving power. This can be accomplished byimplementing and opening a switch in the path of the receiver coilcircuit or disabling the receiver's output or its associated optionalregulator or alike. In this way, only one receiver coil (or moredepending on design and architecture) is at any given time magneticallycoupled to the transmitter and receives power. After some period oftime, that receiver may be disconnected by opening its appropriateswitch and the next receiver powered, etc. Alternatively, one or morereceivers may be powered at the same time. In this case, the receiversmay need to share the available power so for example, while with onereceiver 5 W of output power may be available, with 2 receivers, eachcan only output only 2.5 W, etc. This may be acceptable in many chargingand/or power applications.

In any practical system, in addition to the power transfer andcommunication system, appropriate electromagnetic shielding of thetransmitter and receiver is necessary and may be similar or different tothe tightly coupled systems.

The ratio of the size of the transmitter coil to the receiver coil maybe decided depending on design considerations such as the desired numberof receivers to be powered/charged at any given time, the degree ofpositioning freedom needed, the physical size of device beingcharged/powered, etc. In the case that the transmitter coil is designedto be of a size to accommodate one receiver at a time, the transmitterand receiver coils may be of similar size thereby bringing the looselycoupled system to the tightly coupled limit in this case.

While the loosely coupled system may have distinct advantages and insome ways may overcome the complexities of the multiple coil/moving coilsystems employed in tightly coupled systems to achieve positionindependence, traditional systems suffer from several issues:

(1) Since a large area transmitter coil and smaller receiver coil may beused, Electromagnetic emission in areas of the transmitter coil notcovered by the receiver coil is present. This emission is in the nearfield and drops rapidly away from the coil. Nevertheless, it can haveadverse effects on devices and/or people in the vicinity of thetransmitter.

(2) The receiver may be incorporated or attached to Electronic andelectrical devices or batteries that often contain metallic componentsand/or circuits and/or parts/shells, etc. Such metallic sections thatare not shielded may absorb the emitted EM field from the transmitterand create destructive and undesirable eddy currents and/or heating inthese parts.

(3) The Electromagnetic field emitted may also affect the operation ofthe device being powered or charged or even nearby devices that are noton the transmitter/charger. Such interference with deviceoperation/reception or a drop in sensitivity of a radiotransmitter/receiver (desense) is quite important in design of mobile orelectronic devices such as mobile phones or communication devices. Toavoid this effect, the portions of the device being charged or poweredthat may be exposed to the Electromagnetic (EM) field with the exceptionof the receiver coil area may need to be shielded causing severerestrictions on the device design and affecting operation of otherantennas or wireless components in the device.

(4) In many situations, an after-market or optional receiver such as acase, skin, carrier, battery or attachment with a receiver built in isdesired to enable a mobile or electronic/electric device to be poweredor charged wirelessly. To shield the entire device from EM radiation atlocations beside the receiver coil, such an after-market or optionalreceiver will require shielding in all other locations of the devicethereby severely limiting the design and choices in after-marketproducts possible. For example, a battery with a built in receivercircuit and shielding may not be sufficient to protect a mobile deviceto be charged wirelessly. For example, in the case of a mobile phone,such a battery would cover only a small area of a mobile phone's back'ssurface area leaving the rest of the phone exposed to EM radiation whichcould have serious effects on its performance and operation.Furthermore, the shielding may affect the performance of the device andits multiple wireless components.

(5) Metallic objects such as keys or coins or electronic devices orcameras that contain metal backs or circuits containing metals or othermetal that are placed on a charger/transmitter may affect the operationof the transmitter and draw power from it due to eddy currents. This mayresult in excessive heating of such objects that is highly undesirable.

(6) The EM field emitted from the transmitter further may besufficiently physically close to a user as to be affecting and incidenton the user. Such exposure to EM radiation may result in unwanted orunacceptable levels of exposure.

(7) Many regulatory guidelines regarding the safe exposure limits forhuman and electrical/electronic device operation exists and awarenessand concern regarding this issue is increasing. Any unnecessary exposurefrom an uncovered and operating area of a transmitter is highlyundesirable.

(8) A substantial amount of power from the transmitter may be lost fromthe area that is not physically covered by the receiver leading to lowerefficiencies and wastage of power.

(9) To capture the most amount of power and to achieve higherefficiencies, the receiver coil area must be maximized. This often leadsto a larger receiver coil area than tightly coupled implementations.

It is therefore desired to benefit from the advantages of a looselycoupled system while minimizing or avoiding problems related to it.

In accordance with various embodiments described herein, throughappropriate design of the system, and use of two novel techniquesreferred to herein as Magnetic Aperture (MA) and Magnetic Coupling (MC)respectively, the benefits of the use of a mismatched (in size) coilsystem can be retained, while overcoming the problems and issues raisedabove, leading to ideal systems for wireless power transfer.

As described above, a position independent system may be implemented byuse of a large area transmitter coil upon which a smaller receiver coilmay be placed on a variety or any location and receive power. Typically,a system such as shown in FIG. 2 includes capacitors in series and/orparallel with the transmitter and/or receiver coils to provide aresonant circuit that shows strong power transfer characteristics atparticular frequencies. (See for example S. Y. Hui, H. S. H Chung, andS. C. Tang, IEEE Transactions on Power Electronics, Vol. 14, pp. 422-430(1999), which shows an analysis method for such a system). Using valuesof L1=46 pH for the transmitter coil and L2=4μH for the receiver (basedon a 16 cm×18 cm 13-turn transmitter coil and a 4 cm×5 cm, 6-turnreceiver coil (J. Casanova, Z. N. Low, and J. Lin, IEEE Trans. OnCircuits and Systems—II, Express Briefs, Vol. 56, pp. 830-834 (2009)),and using 12 nF for the receiver capacitance, the impedance to the inputsupply of the transmitter can be calculated as shown in FIG. 14, clearlyshowing the resonance in power transfer 250.

In practice, a transmitter operating on or near resonance frequency doesnot draw much power until a receiver of appropriate inductance andcapacitance is nearby thereby shifting its operating point and bringingit into resonance at which point, significant power can be drawn fromthe transmitter supply and enabling large power transfer and high powertransfer efficiencies. However, as described above, a large areatransmitter typically would also then emit power into areas not coveredby the receiver coil, which could cause EMI and accompanying healthissues.

In accordance with various embodiments, the techniques described hereinallow operation of a position-independent power transfer system, whilereducing or eliminating undesirable radiation from other areas of thetransmitter coil. To achieve this, it is necessary to achieve theseemingly mutually exclusive conditions of low-to-no emission from atransmitter coil, with high-efficiency and position-independenceoperation at positions with the presence of the receiver coil. Ideally,this system is passive in that no complicated detection of receiverlocation and switching and control of the power transfer is necessary.

In accordance with an embodiment, a large transmitter coil and smallerreceiver coil or coils similar to a loosely coupled system are used.However, to reduce or eliminate radiation from the transmitter coil, thetransmitter coil is covered with a thin soft magnetic layer.

FIG. 15 shows the magnetization curves 260 of a number of Ferromagneticmaterials. They include (1) Sheet steel, (2) Silicon steel, (3) Caststeel, (4) Tungsten steel, (5) Magnet steel, (6) Cast iron, (7) Nickel,(8) Cobalt, and (9) Magnetite. In the linear regime of operation, themagnetic field strength H is related to the magnetic flux density Bthrough the permeability of the material μ:

B=μH+M

where M is the magnetization of a material. It must be noted that B, H,and M are vectors and μ is a scalar in isotropic materials and a tensorin anisotropic ones. In anisotropic materials, it is therefore possibleto affect the magnetic flux in one direction with a magnetic fieldapplied in another direction. The permeability of Ferromagneticmaterials is the slope of the curves shown in FIG. 15 and is notconstant, but depends on H. In Ferromagnetic or Ferrite materials asshown in FIG. 15, the permeability increases with H to a maximum, thenas it approaches saturation it decreases by orders of magnitude towardone, the value of permeability in vacuum or air. Briefly, the mechanismfor this nonlinearity or saturation is as follows: for a magneticmaterial consisting of domains, with increasing external magnetic field,the domains align with the direction of the field (for an isotropicmaterial) and create a large magnetic flux density proportional to thepermeability times the external magnetic field. As these domainscontinue to align, beyond a certain value of magnetic field, the domainsare all practically aligned and no further increase in alignment ispossible reducing the permeability of the material by orders ofmagnitude closer to values in vacuum or air.

Different materials have different saturation levels. For example, highpermeability iron alloys used in transformers reach magnetic saturationat 1.6-2.2 Tesla (T), whereas ferromagnets saturate at 0.2-0.5 T. One ofthe Metglass amorphous alloys saturates at 1.25 T. The magnetic field(H) required to reach saturation can vary from 100 A/m or lower to1000's of A/m. Many materials that are typically used in transformercores include materials described above, soft iron, Silicon steel,laminated materials (to reduce eddy currents), Silicon alloyedmaterials, Carbonyl iron, Ferrites, Vitreous metals, alloys of Ni, Mn,Zn, Fe, Co, Gd, and Dy, nano materials, and many other materials insolid or flexible polymer or other matrix that are used in transformers,shielding, or power transfer applications. Some of these materials maybe appropriate for applications in various embodiments described herein.

FIG. 16 shows the hysteresis curve 270 for a hard ferromagnetic materialsuch as steel. As the magnetic field is increased, the magnetic fluxsaturates at some point, therefore no longer following the linearrelation above. If the field is then reduced and removed, in some media,some value of B called the remanence (Br) remains, giving rise to amagnetized behavior. By applying an opposite field, the curve can befollowed to a region where B is reduced to zero. The level of H at thispoint is called the coercivity of the material.

Many magnetic shield layers comprise a soft magnetic material made ofhigh permeability ferromagnets or metal alloys such as large crystallinegrain structure Permalloy and Mu-metal, or with nanocrystalline grainstructure Ferromagnetic metal coatings. These materials do not block themagnetic field, as with electric shielding, but instead draw the fieldinto themselves, providing a path for the magnetic field lines aroundthe shielded volume. The effectiveness of this type of shieldingdecreases with the decrease of material's permeability, which generallydrops off at both very low magnetic field strengths, and also at highfield strengths where the material becomes saturated as described above.The permeability of a material is in general a complex number:

μ=μ′+hjμ″

where μ′ and μ″ are the real and imaginary parts of the permeabilityproviding the storage and loss component of the permeabilityrespectively. FIG. 17 shows the real and imaginary part of thepermeability of a ferromagnetic material layer 280.

FIG. 18 shows the Magnetization curves 290 of a high permeability (realpermeability ˜3300) proprietary soft magnetic ferrite material at 25° C.and 100° C. temperature. Increase of temperature results in a reductionin the Saturation Flux density. But at either temperature, saturation ofthe flux density B with increasing H is clearly observed. A distinctreduction in the slope of B-H curve (i.e. material permeability) isobserved at around 100 A/m and the reduction of the permeabilityincreases with H increase until the material permeability approaches 1at several hundred A/m. This particular material is MnZn based andretains high permeability at up to 1 MHz of applied field frequency butloses its permeability at higher frequencies. Materials for operation atother frequency ranges also exist. In general, MnZn based materials maybe used at lower frequency range while NiZn material is used more athigher frequencies up to several hundred MHz. It is possible withappropriate material engineering and composition to optimize materialparameters to obtain the desired real and imaginary permeabilities atany operating frequency and to also achieve the saturation magneticfield and behavior desired.

Magnetic Coupling (MC) Geometry

In accordance with various embodiments, a method can be provided forshielding/reducing the EM field emitted from the transmitter coil, whileat the same time providing a path for transfer of power from this fieldto a receiver coil placed arbitrarily on the surface of the transmitter.To achieve this, in accordance with an embodiment 300 shown in FIG. 19,a large area transmitter coil (of wire, Litz wire, or PCB type, or acombination thereof) is covered by a ferromagnetic, ferrite, or othermagnetic material or layer that acts to guide, confine, and shield anyfield, due to its high permeability. Choosing the thickness of thematerial and its permeability and saturation properties, the magneticmaterial can reduce or shield the field in the area above thecharger/transmitter coil so that it is reduced by 2 orders of magnitudeor less compared to an otherwise similar geometry without the magneticlayer. Bringing a receiver coil with appropriate resonant capacitor inseries or parallel to the receiver coil, the field penetrating themagnetic layer can be collected, and localized power transfer whereverthe receiver coil is placed can be achieved.

To test this geometry, a charger coil similar to shown in FIG. 12 with asize of 18 cm×18 cm consisting of Litz wire was created and covered witha 0.5 mm thick sheet of material with properties shown in FIG. 17. Acircular receiver coil of 7 turns with radius 2 cm was placed on top ofthe charger surface/magnetic layer. This Magnetic Coupling (MC) geometry320 is shown in FIG. 20. The receiver circuit comprises a parallelresonant capacitor, followed by a bridge rectifier and smoothingcapacitor. Significant power transfer was achieved with receiver coil atdistances of several mm to 2-3 cm from the charger surface. The powertransfer and efficiency increased with introduction of a 0.5 mm thickferrite magnetic material or layer above the coil to guide and shieldthe flux as shown in FIG. 20. The resonance of the charger/receivercircuit in this case is important for operation of the MC configuration.The leakage field from the surface of the charger can be reduced byusing thicker or higher permeability magnetic layer. Choosing theappropriate magnetic layer and receiver shield/guide layerpermeabilities and thicknesses is important to provide a low reluctancepath for the magnetic flux to allow higher power transfer andefficiencies while achieving sufficient field shielding at otherlocations of the charger. The inventors have found that power transferof over 10 W at the output and DC-out to DC-in power transferefficiencies of over 50% can be achieved in this MC configuration withseveral mm to 2-3 cm of charger/receiver coil distance. Moving the MCreceiver coil laterally across the surface of the transmitter coilconfirms that high power transfer and high efficiencies can be obtainedacross the transmitter surface. The amount and efficiency of the powertransfer showed very good uniformity. The emission from other locationsof the charger, where the receiver was not present, were monitored by aprobe and shown to be lower by 2 orders of magnitude or more compared tosimilar locations in a magnetic resonant charger with no magnetic layer.Due to the high permeability of the ferrite layer, this fringing(leaking) field dies away rapidly from the top surface and should notcause significant EMI issues away from the charger. No interferenceeffect with magnetic or non-magnetic metal sheets or ferrites placed onthe charger surface were observed, showing that the magnitude of theleakage field from the surface is small and only couples well to thereceiver due to the resonant conditions produced by the receiver LCcircuit. Also as expected, multiple receivers could be charged/poweredsimultaneously in this MC geometry.

In accordance with an embodiment in the MC geometry, the reluctance ofthe flux path in the receiver can be lowered by including highpermeability material in the core of the receiver ring coil (similar toa solenoid) or a T-shape core or alike. Many geometries are possible andthese are only given here as examples. Additionally, while Litz wirereceiver coil was used. PCB coils and/or a combination of Litz wire andPCB coil can be used.

In accordance with an embodiment, to reduce the reluctance of the path,the receiver coil can be created by using a flux guide material (such asferrite with permeability greater than 1) with an axis perpendicular (oran angle sufficient to catch the substantially perpendicular flux fromthe charger) to the surface of the charger. As shown 330 in FIG. 21,Litz wire can be wrapped around the core to create a solenoid typereceiver with a relatively small cross section (2 mm×10 or 20 mm)substantially parallel to the surface of the charger. In one example,the length of the solenoid height (along the direction perpendicular tothe surface of the charger) was varied from 10 to 20 mm but could beshorter. Typical number of turns on the receiver coil was 7 turns.Substantial power transfer (over 20 W) was received at resonance withthe receiver coil bottom on or within several cm of the surface of thecharger. Rotating the angle of the solenoid with respect to theperpendicular direction to the surface to the charger produced largepower transfers confirming that as long as some component of the chargerflux is along the axis of the coil, efficient power transfer can beobtained. Minimal leakage power from other areas of the charger surfacewas observed and position free and multiple receiver operation could beobtained as expected. As shown in FIG. 21, optionally, an additionalshield/guide layer on the top of the receiver and on the bottom of thecharger can also be added. Such a solenoid with a magnetic flux guidecan be constructed to also have a larger area parallel to the surface ofthe charger approximating the embodiment in FIG. 20 but with a fluxguide layer in the middle of the coil. In this case, the height (alongthe length perpendicular to the surface of the charger) can be quiteshort (1-2 mm or less). Use of the flux guide and a smaller crosssection parallel to the surface of the charger as shown in FIG. 21 mayalso be important for applications where small areas for the sections ofreceiver in the plane of the charger are available. Examples may bedevices such as phones, etc. or batteries that are longer in 1 or 2dimensions and would be stood substantially on their ends or sides toreceiver power wirelessly.

In accordance with another embodiment, the charger/transmitter alsoincludes magnetic flux guide layer/shield at the bottom of the chargeras shown in FIG. 20 and FIG. 21 so that emissions from the bottom of thecharger/transmitter are reduced. In yet another embodiment, metal layersare also included on the top of the receiver shield and/or the bottom ofthe charger/transmitter shield to provide further shielding from themagnetic field.

It must be noted that for a transmitter coil of geometry in FIG. 12 withseveral A of current in the coil (currents used here), the incidentmagnetic field is estimated to be in the 100 A/m² to several 100 A/m²range (see FIG. 13). Care must be taken so that the magnetic material ischosen such that magnetic saturation does not occur. However, in theregion of power transfer between the charger and the transmitter coilthe magnetic field is enhanced by the resonance and the Quality Factor(Q) of the system and a much larger magnetic field may be present. Inthese tests, the Q of the system was about 30. Thus it may be possiblethat in the power transfer location under the receiver coil, themagnetic layer can experience saturation and reduction of permeabilityto provide a more efficient path for the flux from the charger coil totransmit to the receiver coil above and increased power transfer andefficiencies. By choosing magnetic layers with appropriate saturationfield values, this effect can be used to benefit as described above.

Magnetic Aperture (MA) Geometry

In accordance with another embodiment and geometry, one can create aMagnetic Aperture (MA) in a magnetic shield or ferromagnetic layer atany desired location, so that the magnetic field confined in such alayer at that location is efficiently coupled to a receiver coil and canprovide power transfer to such a receiver. At any other location on thetransmitter coil, the confinement of the field prevents or reducesunnecessary radiation, thereby providing low EMI and adverse health andinterference effects.

Several methods to enable local change (switching) of thecharacteristics of the ferromagnetic material in the MA geometry aredescribed herein. In accordance with an embodiment, the localcharacteristics of the ferromagnetic, ferrite, or other magneticmaterial or layer are altered by saturating the layer throughapplication of a DC and/or AC magnetic field such as through a permanentmagnet or electromagnet, etc. For example, a magnet or electromagnet canbe incorporated behind, in front, around or at the center of thereceiver coil or a combination thereof such that it has sufficientmagnetic field to saturate or alter the magnetization curve of theferromagnet layer locally on or near where the receiver coil is placed.

Examples of magnets that can be used include, e.g. one or more disc,square, rectangular, oval, curved, ring (340 in FIG. 22), or any othershape of magnet and combination thereof and with appropriatemagnetization orientation and strength that can provide sufficient DC orAC magnetic field to shift the operating position of the magnetizationcurve (as shown in FIG. 15 or FIG. 18), so that the combination of thetransmitter coil, the affected ferromagnet layer and the receiver coilmove to a resonance condition at a given frequency for power transfer.

As shown in FIG. 23, in accordance with an embodiment 350 of MA, byincorporating a permanent (and/or electromagnet) into the receiver infront, and/or behind and/or at the level of the receiver coil (on theoutside and/or inside of the coil), and bringing the receiver close tothe charger surface, at this point, a local ‘magnetic aperture’ isopened up in the ferromagnetic, ferrite, or other magnetic material orlayer, allowing the transmitter coil's electromagnetic field to betransmitted through this local aperture without affecting any areasnearby. In this manner, by reducing the permeability of the ferromagnetlayer locally through saturation or reduction with the DC and/or ACfield or other means, one can establish at what location the power andenergy coupling occurs while keeping the field confined in other areas.The magnetic or ferrite material layer is here therefore alsoalternatively called a switching layer. This layer acts as both areservoir and/or guide layer of AC magnetic flux (for power transfer)and a switching layer. This embodiment can be used to meet the goal ofsimultaneously transferring power efficiently to a receiver at anydesired location while keeping the field from emitting at otherlocations and causing problems. At the same time, since the magneticfield created from the entire surface of the charger coil is directed orguided towards the magnetic aperture created, this provides an effectanalogous to funneling the power to this magnetic aperture area and anefficient method for transfer of power to an arbitrarily positionedreceiver is achieved. In FIG. 23, typically, the receiver may alsoinclude an outer surface or case. Such a surface or case would betypically located between the receiver coil and the charger surfaceparts as shown in FIG. 24.

FIG. 24 provides an illustrative method of understanding the behavior360 of the system. Magnetization curves of a soft ferrite material areshown at different operating temperatures. The AC magnetic fieldgenerated by the wireless charger/power supply coil is also shown in tworegions of operation (shielded region and the magnetic aperture region).Most of the surface area of the ferrite layer has no receiver on it andoperates in the shielded region with high permeability guiding andshielding the AC magnetic field generated by the charger/power supplycoil in the transmitter from the outside. In the magnetic apertureregion (where the receiver and the switching magnet is), the DC (and/orAC) magnet acts as a bias to move the operating point from around thevertical axis where the material has high permeability and confines andguides the magnetic field to a region where the material is saturatedand has a low permeability creating a magnetic aperture for coupling toa receiver coil nearby causing efficient power transfer. The magneticfield required for saturating the switching material (the magneticswitching field) can be easily created by many types of commonlyavailable magnets that can generate up to several 100's of A/m or moreof magnetic field easily saturating many ferrite materials.

As can be seen above, this approach utilizes the physics underlying thenonlinear behavior of ferrite material to act as an active switch toprovide power transfer only in desired locations. Permeability is aninherent material property of a magnetic material and the response timeof the material is only limited by domain movements and can be in nanoseconds or faster depending on the material. It is therefore one of theadvantages of this system that the device responds almostinstantaneously, and, if a receiver is moved on the surface, a newaperture is created and shielding is restored at all other locationsalmost instantaneously. In comparison, any other wireless charger systemsuch as coil arrays, moving coils, etc. has a slow response to suchmovement due to time lag related to mechanical movement of coil and/orelectronic detection and reconfiguration of an electronic system.Furthermore, multiple receivers (with switching magnets) can be placedon or near the charger surface to create multiple magnetic apertures forcoupling of power to multiple receivers while maintaining shielding andlow electromagnetic emission at all other locations providing a simpleto use, efficient multi-charger system.

In accordance with an embodiment, to provide shielding from the magneticfield at locations below the transmitter coil (the side opposite to thecharging/power side of the transmitter) and above the receiver coil (onthe side of the coil that may be in close contact with a device,battery, or electrical part being powered or charged wirelessly),further shielding layers such as ferromagnet and/or metallic layers canalso optionally be added below the transmitter coil and/or above thereceiver coil as necessary. Furthermore, these layers can be integratedinto the coil design (such as metal shield layers integrated into a PCBmulti-layer design that includes a PCB coil). The choice of material andthickness, etc. can be chosen such that even though a magnet in thereceiver may be used to saturate (switch) the top layer of thetransmitter (the switching layer), the permeability of the shield layerswould not be affected. For example, the switchable layer in the chargercan comprise material with low saturation field values while the othershield layers in the charger and/or receiver have higher saturationfield values. Examples of materials to use for these shields may besheets or other shapes of material such as ferrites, nano materials,powder iron (Hydrogen Reduced Iron), Carbonyl Iron, Vitreous Metal(amorphous), soft Iron, laminated Silicon Steel, Steel, etc. or othermaterial used in transformer core applications where high permeabilityand saturation flux densities as well as low eddy current heating due toconductivity at frequency of operation is required. Lamination has alsobeen used in many applications of transformers to reduce eddy currentheating. It must be noted that to avoid saturating the ferrite shieldfrom the switching magnet in the receiver, the shield can also bemulti-layer or other structures can be used. For example in anembodiment, a thin high saturation flux density layer (of for examplepowdered Iron or steel) can be placed behind the switching magnet (asshown in FIG. 23) to shield from the switching magnet field with anotheroptional ferrite layer of other characteristics such as higherpermeability or operation at the AC magnetic field frequency above that.Thus, the high saturation flux density layer will shield the highpermeability layer from the saturating effects of the magnet and allowit to guide and shield the AC magnetic field effectively.

In another embodiment, the high saturation shield layer is formed ormanufactured to have a shape and dimensions to fit the magnet'sswitching magnetic field pattern to shield the field from it and allowthe AC power magnetic field from the charger that is coming through thecreated magnetic aperture to extend upwards (in FIG. 23) to anothershield or ferrite layer with different characteristics. For example inthe geometry of FIG. 23, if a ring type of switching magnet is used, thehigh saturation shield material may be ring shaped with appropriatedimensions and placed behind (atop in FIG. 23) of the magnet to shunt orreduce the field from the magnet and a sheet of ferrite is placed on topof the high saturation shield layer to guide and shield the AC magneticpower transfer flux coming through the center of the coil as shown inFIG. 23. Many combinations of the above techniques and materials can becombined in the receiver and charger to best optimize performance andthese embodiments are only given as examples.

To test the above embodiment, a transmitter coil with Litz wire withdimensions of 10 cm×10 cm was constructed. The coil was constructedsimilar to earlier work (J. J. Casanova, Z. N. Low, J. Lin, and RyanTseng, in Proceedings of Radio Wireless Symposium, 2009, pp. 530-533 andJ. J. Casanova, Z. N. Low, and J. Lin, IEEE Transactions on Circuits andSystems—II: Express Briefs, Vol. 56, No. 11, November 2009, pp.830-834). The receiver comprised a Litz wire coil of 35 mm radius and 10turns and the received power was connected to a rectifier and capacitorcircuit to provide a DC output. The transmitter coil was then drivenwith a resonant converter circuit similar to FIG. 2 and the frequency ofthe system was adjusted for test purposes. It is important to realizethat different power delivery mechanisms and receiver systems as well asdifferent shape, geometry, winding, and construction of coils such aswire, Litz wire, or a combination can be used, and this setup is usedonly as an example.

To test the transmission capability of the loosely coupled system itselffirst, a resonant converter wireless charger drive circuit was poweredfrom a DC supply at 20 V input voltage and the receiver coil was placedon the transmitter with a coil to coil vertical (z-direction) gap of 5mm. Power level in excess of 20 W with a DC output to DC input poweroverall system efficiency of over 70% could be achieved. When moving thereceiver coil power laterally, power transfer was observed across thesurface of the charger. However the amount and efficiency of the powertransfer at a fixed drive frequency was not uniform. Placing a metalobject, such as a metal disk, on the transmitter surface at a locationlaterally away from the receiver coil confirms that strong magneticfield emissions exist on the entire surface of the transmitter coil asexpected since the coin heats up within seconds to very hightemperatures confirming heating by eddy currents. Placement of largermetal sheets would shift the resonance frequency significantly and ifbrought back to resonance would heat up the sheet through eddy Currents.Similarly, a receiver circuit connected to some Light Emitting Diodes(LEDs) shows significant power being emitted from all areas of thetransmitter coil as expected.

Next, a sheet of Hitachi material MS-F comprising 18 μm of FineMET®FT-3M material on an adhesive tape substrate was used as aferromagnet/ferrite material (switchable layer) and placed on the entiretop of the transmitter coil surface. This material has a saturation fluxdensity of 1.23 T. Placing a receiver coil 5 mm away from thetransmitter coil and the switchable layer and adjusting the transmitterfrequency, no power was transferred to the receiver at any frequency.Next, a Nd rare-earth ring magnet (of material N45H) of inner diameterof 32 mm and outer diameter of 36 mm and 2.5 mm thickness and magnetizedalong its axis (with North and South pole on top and bottom of the ring)was placed behind in the center of the receiver coil. The ring magnet asshown in FIG. 22 includes a cut or gap in its circumference. This cut orgap is optional and can be manufactured during casting of the magnet toavoid or reduce generation of any eddy currents from stray magneticfields in the receiver in magnetic material that is electricallyconductive (such as Nd rare-earth magnets) during operation in thewireless power system. By breaking the circular pattern of the ring, anypotentially generated currents would not be able to circulate and heatthe magnet.

The overall geometry 370 of the MA for operation with the switchablelayer and the receiver and magnet is shown in FIG. 25 for two receiversof dissimilar size and possibly power ratings and/or voltage outputs.FIG. 25 shows a simplified side view of a wireless power system inaccordance with an embodiment, showing a charger (transmitter) andreceiver coil, switching layer, and switching magnet. In this instance,a ring switching magnet is shown and the coils are described as circularring coils for simplicity. However, in accordance with otherembodiments, other geometries and designs can be used to achieve similarresults. For example, as described above, the coil can be configured toachieve a more uniform field pattern and/or the magnet can be of adifferent shape and magnetization orientation. In addition, the magnetcan be placed in front of, behind, or on the same plane as the coiland/or the coils can be made of wires, PCB, free standing metal parts ora combination thereof or other geometries and materials.

The magnetic flux densities and the magnetic field orientation are alsoshown in FIG. 23. The magnetic flux flows or is guided in the switchinglayer and is funneled or directed to the receiver location by thepresence of the receiver magnet. The arrows for the AC magnetic fluxdensity lines are shown to guide the reader in the direction of theenergy flow rather than show the vector direction since this field is ACand changes direction in every half cycle.

In an isotropic material, the switching magnetic field (from theswitching or permanent magnet or electromagnet shown here) should have acomponent in an orientation along the direction of the AC (wirelesspower transfer) magnetic field to saturate the permeability in thatorientation and affect its behavior. However, in an anisotropicmaterial, different orientations of switching magnetic field can affectthe permeability along the plane of the ferrite layer affecting the ACmagnetic power transfer field, giving rise to interesting combinationsof switching layer materials and magnet designs to achieve enhancedperformance.

In the embodiment shown in FIG. 23, and using a ring magnet as theswitching magnet, due to overlap of the radial orientation of themagnetic field from the ring magnet magnetized axially (North and Southpoles along its axis which is perpendicular to the plane of the chargersurface), the DC switching magnetic field is parallel to the x-y planeunder the ring magnet and more vertical in the center of the ring magnetso it is oriented to efficiently direct the AC wireless power magneticfield in the region towards the created aperture for power transfer.However, alternate geometries such as an arc, radially magnetized ring,cylinder, or multi-pole magnets can be used to provide optimal powercoupling. A multi-pole magnet can provide a tighter external magneticfield pattern and may reduce any potential unwanted effect of magnet onnearby devices/materials while providing sufficient magnetic field tosaturate the switching layer. In addition, use of appropriately designedmagnets and/or anisotropic or multi-layer switching layers can result inenhanced switching performance and coupling of power with minimalswitching magnet strength.

In accordance with another embodiment, multi-pole magnets that havestrong magnetic field strengths near the surface of the magnet withrapidly decreasing magnetic field strength away from the surface can beused. Some examples of multi-pole magnets are shown 380 in FIG. 26. Suchmagnets can provide magnetic aperture switching nearby, whilemaintaining weak magnetic field strengths farther away, therebyminimizing the effect on other materials, devices, etc. This feature maybe especially important for use with devices such as GPS or compassesthat use the weak magnetic field of the earth to detect the deviceorientation.

In accordance with one embodiment that uses a ring magnet as shown 390in FIG. 27, the magnet can be magnetized radially or along its axis, butcan comprise multiple alternating poles. Some examples of ringmulti-pole magnets magnetized axially (perpendicular to the plane here)(a) and radially in the plane (b) and along directions shown by arrowsin (c), (d), and (e). Different magnetic flux lines can be obtained(shown in (c), (d), and (e)) can be obtained depending on theorientation and number of poles and can be optimized to provide an idealmagnetic aperture and coupling between the flux lines of the chargercoil and receiver coil providing optimum efficiency. As an example, themagnet shown in FIG. 27(e) which consists of multiple sections poled ina particular geometry as shown provides uniform in plane magnetic fluxlines in the center of the magnet to create a uniform magnetic aperturein the FIG. 23 geometry while producing minimal fields outside themagnet. The geometries shown here are not meant to be exhaustive butshow that many possibilities for design and optimization of the magnetsexist and can provide optimum coupling in the smallest possible area.

In accordance with an embodiment, in addition to reduce or eliminateeddy currents, a cut or gap in the circumference of a ring, square, orother type of magnet can be introduced to prevent circular current fromflowing due to the alternating magnetic field. FIG. 28 shows twoexamples 400 of multi-pole ring or arc magnets with cuts or gaps in thecircular pattern, in accordance with various embodiments.

While the magnetic field necessary to saturate the switching layer canbe engineered to be switched with low magnetic strength magnets that ingeneral would not pose any problems to the device or any objects nearby,in accordance with another embodiment, to reduce or eliminate anypotential effect of the switching magnet's magnetic field on thedevice's performance, its compass or GPS or on nearby devices orobjects, magnetic shielding material such as shown on the top and bottomin FIG. 23 can be incorporated in the receiver behind the magnet (top ofFIG. 23).

In addition, the device, case, skin, battery door or batteryincorporating the receiver and the switching magnet may incorporate acomponent that would shunt the switching magnet's magnetic flux andshield it from penetrating out from the surface of the device, skin,battery door, or battery. An example would be a cover manufactured fromsheet of ferrite, magnetic material, magnetic steel, Alnico, Permalloy,etc. or a combination thereof that would be normally placed or attached,slid on or held on the outside area of the magnet (lower part of thereceiver in FIG. 23) while the device is being used normally. This covercould be slid open, removed or detached to expose the magnet beforeplacement of the device, case, skin, battery door or battery, etc. on ornear the charger surface to commence charging. The cover can alsosimultaneously have a shielding layer sheet that normally would shieldthe switching magnet from the interior of the device and would also beslid aside to allow normal operation of the receiver without these highpermeability magnetic flux shunt layers. Alternatively, the switchingmagnetic field can be generated by an electromagnet in the receiver bypassing a DC or AC or a combination of currents through anelectromagnet. This may be activated mechanically by the user or througha detection mechanism that detects approach of a wireless chargerthrough various RFID, NFC, Bluetooth, Felica, WiFi, optical, or other RFor wireless detection, and applies the appropriate power to theelectromagnet in preparation for receiver to be placed on the wirelesscharger. Alternatively, the switching magnetic field may also be createdby a combination of a permanent and electromagnet fields. Alternatively,the cover layer described above for a permanent magnet can beautomatically slid open, removed, opened, etc. when a charger isdetected nearby through RFID, NFC, Bluetooth, Felica, WiFi, or other RF,wireless, or optical or magnetic detection mechanisms.

In accordance with an embodiment, to bring the system to resonance, thefrequency of the applied power to the charger coil can be adjusted toobserve power transfer through the switchable MA layer. Experimentally,with a single magnet for switching no power transfer was observed.Doubling the magnet strength by double stacking the magnets providedsufficient magnetic field strength to saturate the switchable layer andadjusting the frequency, large amounts of power were transmitted throughthe opened aperture. Over 10 W of power and efficiencies in excess of upto 50% were achieved. To achieve optimum power transfer, it is necessaryto move the magnets some distance (e.g. about 25 mm vertically in thez-direction) away from the transmitter surface. This may be due to themagnet size (diameter) being much smaller than the receiver coil and tosaturate the switchable layer with sufficient size to optimally couplepower to the receiver coil, it was necessary to move the magnets away toallow their fringing fields to be larger in area than the size of themagnets itself and thereby open an optimally sized aperture for powertransfer. In accordance with other embodiments, a larger diameter magnetthat is matched with the receiver coil size can be used and can be atthe same plane as the receiver coil (inside, outside or behind thereceiver coil).

In accordance with an embodiment, the magnetic flux density of eachmagnet was estimated to be around 1.3 T by the manufacturer. Inpractice, it was observed that doubling up the magnets by stacking ontop of each other and moving the magnets away to optimally match theaperture size to the receiver coil was optimal for power transfer. Thisis understandable in view of the fact that while the single magnetshould have sufficient magnetic field to saturate the layer close to itssurface, the resulting aperture when the magnet is on the plane of thereceiver coil and close to the transmitter coil and switchable layer (5mm distance between magnet and the switchable layer) is comparable insize to the magnet and smaller than the 40×50 mm size of the receivercoil. To achieve the best coupling, the magnet had to be further away(25 mm between magnet and transmitter switchable layer) in this exampleand therefore 2 magnets were required to provide sufficient flux densityin this example. Even with the magnet co-planar with the receiver coil,doubling the magnets was necessary to provide sufficient fringing fieldsto open a sufficiently dimensionally large aperture for efficient powertransfer.

In accordance with an embodiment, changing the receiver coil size sothat it is comparable to the switching magnet diameter provides moreefficient coupling, with output to input power efficiencies of 50% toover 70%, and output power levels of over 25 W achieved with even asingle magnet due to better switching magnet field overlap with thereceiver coil.

In accordance with an embodiment, due to the circular symmetry of thegeometry used, the receiver can be rotated in the plane without anychange in the received power or system efficiency. Rotation of thereceiver out of the plane also demonstrated sizeable power transfer.

To test emission levels from other areas of the transmitter, the testwith metallic object was repeated by placing a metallic object at alocation close to the receiver coil on top of the transmitter surface.No change in power coupled to the receiver and no appreciable heatingwas detected. Similarly, when the magnets were removed from the centerof the receiver coil, the power transfer stopped and the transmitteronly drew very minimal current (less than 100 m A). While with themagnets at the center of the receiver coil, the transmitter drew 1 A ormore of current. This is a very dramatic and large confirmation of theprinciple described here.

As a further test, the magnet and receiver were placed on a location onthe transmitter coil (covered with a switching layer on top of it).Large current draw from the transmitter power supply can be observed atan adjusted resonant frequency. This is due to the power being emittedthrough the generated magnetic aperture (MA) into the receiver. Next,another receiver coil without a magnet was placed on the transmitter ata location near the first receiver and magnet. No discernible powertransfer was detected in this MC geometry. This is presumably due to thefact that the 2 locations have different inductance values and resonateat different frequencies. However, it may be possible to have both typesof receivers operate on a single type of charger if the resonantconditions of the 2 different receivers are moved to be at the samefrequency. This may be achieved by adjusting the resonant conditions ofthe 2 receivers by adjusting their LC circuit with adjusting theresonant cap (or a parallel or in series adjustable inductor) in thereceiver. Moving the MA receiver coil (with switching magnet) laterallyacross the surface of the transmitter coil confirms that high powertransfer and high efficiencies can be obtained across the transmittersurface. The amount and efficiency of the power transfer showed verygood uniformity.

To confirm that the effect observed is due to the magnetic field and notthe presence of the ferrite material in the magnets, the ring magnetswere replaced with a ring constructed of the same material as the ringbut not magnetized. No power transfer was observed with such a set up.

As a further confirmation, the receiver coil was placed on thetransmitter coil and switchable layer but the magnet was removed. Nextthe magnets were brought close to the transmitter coil from below (theside opposite to the receiver coil). At about 25 mm distance to theswitchable layer, with the magnets aligned with the lateral location ofthe receiver coil, strong power transfer and high power transferefficiency was observed. Moving the magnets laterally away from lateralalignment with the receiver coil, the aperture closed and no power wastransferred further confirming the effect as being due to the field.

As a final confirmation, with the receiver coil and the ring magnetsplaced on the transmitter coil and transmitter frequency optimized forhigh power transfer, a single ring magnet was brought to lateralalignment from below the transmitter coil with the top magnets. With themagnetic poles oriented so that the fields from the below magnet wasopposing the magnetic field from the magnet above, lower amounts ofpower transfer were achieved. Demonstrating that the net magnetic fieldvalue was reduced by half and therefore the aperture was partiallyclosed. Doubling the magnet below the transmitter coil, with the 2magnetic fields from the magnets above and below the transmitter coiland the switchable layer cancelling each other out, the aperture couldbe closed and no power transfer was observed. Flipping the polarity ofthe magnets below the transmitter coil so that the fields from magnetsabove and below would add up on the plane of the ferromagnetic layer,the power transfer would resume.

The multiple tests above appear to confirm that the principle ofoperation is the saturation of the ferromagnetic switchable layer, andthis combination of materials and geometry performs as planned. Namely,safe (low or no EM emission from the surface of the charger/transmitter)and efficient power transmission to a receiver placed at any location onthe transmitter coil can be achieved with minimal side effect andresidual emission.

The embodiments for MC and MA configuration discussed above are notmeant to be exhaustive and many variations and/or combinations of theconfigurations are possible. Overall, the transferred powers and theefficiencies observed from the MA configuration were larger than the MCconfiguration. However, by modeling and judicious design of geometry andmaterials, similar performances may be possible. The communication andcontrol of these system can be similar to the tightly coupled systemsdescribed earlier providing regulation and control between transmitterand receiver. Alternately, the system can be designed with no regulationat the charger, and all the regulation instead at the receiver, or anycombination of architectures as described earlier for loosely-coupled ortightly-coupled wireless power transfer systems above. The wirelesspower transmission systems and methods described herein have idealcharacteristics for this application. By using the magnetic coupling(MC) or magnetic aperture (MA) technique, all the advantages of aloosely coupled system can be retained while achieving high efficiency,high power transfer efficiency, low EMI, and low or no interaction withnearby metallic objects of a tightly coupled system providing an idealsolution.

In practice, with the thin layer of the Hitachi switchable materialused, some heating of the switchable layer was observed. This can be dueto the material being lossy (high imaginary permeability) and/or beingextremely thin. Use of ferrites with minimal or no loss at the frequencyof interest would improve this effect. Also, as noted above and shown inFIG. 15, ferrite material would have significantly lower saturation fluxdensities (0.2-0.5 T) compared to the thin sheet of the FineMET®material used. Thus, smaller magnetic flux densities (smaller or weakermagnets) can be used for switching.

Next to test MA configuration further, an 18×18 cm transmitter coil ofthe shape similar to FIG. 12 was constructed and 60×60×0.5 mm plates ofa MnZn Ferrite material were placed side by side in a tile manner tocover the transmitter coil surface as the switchable material while thesame tests above were performed. This material has a low loss up toabout 100 kHz and a real permeability of about 2000 up to 100 kHz.Similar switching results were obtained with a receiver of about 35 mmdiameter and a single ring switching magnet magnetized along axis asdescribed earlier (FIG. 22). However, with such thicker and lower lossmaterial, no switching layer heating was observed. Adding a resonantcapacitor in parallel to the coil in the receiver of appropriate value,power transfer of up to 30 W into one coil and DC-out to DC-in totalpower transfer efficiencies of over 70% were observed. Many ferritematerials with differing magnetic properties exist and optimizing thevarious fundamental properties and dimensions of the switchable layer orlayers can be performed with more detailed modeling. In general,Furthermore, it is found that with appropriate design and selection ofcoils, switching magnet size, shape and strength and switching layer,the receiver coil can be placed several mm to several cm over thecharger surface and receive power efficiently through a locally openedmagnetic aperture. So the operation is not limited to the receiver beingin direct or close contact with the charger surface.

In accordance with an embodiment, it may be advantageous to constructthe charger/transmitter coil from ferromagnetic material withappropriate property so that the coil acts as both the magnetic fieldgenerator and the magnetic shield for MA and MC geometry. This mayeliminate the need to have an additional magnetic or ferrite layer onthe top surface of the charger/transmitter. Alternately, to retaindesirable high conductivity and Q of the transmitter and/or receivercoils and to achieve the switching effect, a metallic coil of PCB and/orwire may be coated or covered with a switching magnet material such asferromagnet. FIG. 29 shows a commercially available wire or cable 410available in a variety of gauges with these characteristics. Section 1in FIG. 29 consists of multiple strands of copper or other conductorwire which may also be individually coated or insulated to avoidconduction between the strands (similar to Litz wire) to avoid skineffects. Section 2 is an overcoat or layer of ferrite or other magneticmaterial. Section 3 is an optional outer coating or insulation. Theferrite layer or coating can be achieved by dipping into a slurry,sputtering, e-beam, etc. as appropriate.

Similarly, a magnetic or ferrite layer made of material with lowsaturation magnetic field values can be used above the transmitter coil(for example as switching layer in MA or even MC geometry) while amaterial with higher saturation magnetic field value can be used belowthe transmitter coil and above the receiver coil for shielding purposes.For example, Nickel, cobalt, Mn, Zn, Fe, etc. or alloys of such material(see FIG. 15 or FIG. 17) with low saturation magnetic field values maybe used as the top layer of the charger/transmitter while Sheet Steel orFineMET® or other shield material with high saturation magnetic fieldvalues would be used for shielding. For either material, care must betaken to use material that reduces or eliminates eddy currents throughgeometry or doping of the material to provide high resistivity. By usinga low saturation magnetic field material, a smaller and/or weakerswitching permanent magnet and/or electromagnet induced field may beused for switching the switchable layer in the MA geometry. Thus, theshields would not be saturated by the magnet used for switching andwould remain effective in shielding unwanted stray magnetic fields fromaffecting nearby devices, materials, or living tissue. In such a case,the total system would be completely shielded and safe. Power would atthe same time transferred efficiently between the transmitter andreceiver from the created magnetic aperture at one or more locationsdesired by user where receivers are placed.

Another type of material that responds strongly to an applied magneticfield is a class of material known as ferrofluids which are colloidalsuspensions of ferromagnetic particles or nano materials in a carrierfluid. In an embodiment the magnetic layer covering the charger coil inthe systems described here may be a layer of ferrofluid materialsandwiched between two barrier layers. With the application of anappropriate switching magnet of the receiver or a local increase in theAC magnetic field, the ferrofluid would be attracted and alignedappropriately to provide a local magnetic variation in the magneticlayer covering the charger coil and allow better coupling between thecharger and receiver coil. Thus a similar behavior to using Ferrites formagnetic layer may be obtained.

The tests above with magnets placed above and below the switching layerin the MA configuration also show that novel methods of switching thelayer can be employed. Since the layer responds to the net totalmagnetic field, a bias magnetic field can be designed to be incident onthe layer and by including a weak additional magnet into the receiver,the total magnetic field with the receiver present can then be designedto exceed the saturation level to switch the layer locally. For example,a bias magnet material or electromagnet in the charger/transmitter canprovide a uniform or local magnetic field to bring the DC or average AClevel close to saturation and a smaller magnet material or electromagnetin the receiver can be used to exceed the required saturation levellocally to open an aperture for power transfer. The bias magnet materialcan be a sheet of permanent magnet (perhaps even flexible plasticmagnets readily available) and/or an electromagnet that would providethe DC bias.

In accordance with any of the embodiments described here, many types ofmagnets may be used to create the switching field in the MAconfiguration. They include metallic, alloy, rare earth, ceramic,ferrite, nano material, Alnico, composite or other material used tomanufacture magnets.

In addition, it must be noted that when power is being transferredthrough the magnetic aperture, an AC magnetic field due to the inductivefield is present. This field may be quite large in a resonant geometrywith a high Q where the power resonating between the coils is largerthan the transferred power by a factor of Q (quality factor).

In accordance with an embodiment, it may be possible to open a magneticaperture with a DC or AC magnetic field from a permanent magnet orelectromagnet from the receiver or a bias DC or AC magnetic field plus amagnet and/or electromagnet from the transmitter/charger and start thepower transfer through an aperture. Once power transfer is achievedthrough such an aperture, the saturating magnetic field may be removedor reduced and if the average value of the AC magnetic field issufficiently high to saturate the layer, power transfer will continue.It must be noted that once an aperture is opened, due to resonance andlocal change of the permeability, the magnetic field at this location ismuch higher than neighboring areas and with proper design and choice ofmaterials and fields, Q, etc, this aperture may be designed to remainopen while the rest of the ferromagnetic layer would remain in a highpermeability state and continue to provide shielding at other locationsand limit radiation from these locations as desired. Such a latchingbehavior was observed experimentally with another type of thin layerferromagnetic material with lower saturation flux density. In addition,the possibility of opening the magnetic aperture through power ACmagnetic field alone without the need for any DC or AC switchingmagnetic field was discussed in the MC section earlier.

In yet another embodiment, the transmitter periodically or continuallyapplies a DC or AC magnetic field generated by a coil (the same ordifferent from the power transmitter coil) and sufficient magnetic fieldto bias the switching layer near or above its saturation value. Thepresence of the receiver coil with or without additional magnetic fieldfrom a permanent magnet or electromagnetic near the transmitter at alocation on the surface may then be sufficient to bring the system toresonance, open the aperture and start power transfer as describedabove. Once power transfer starts, then the bias field may be removed orlowered to save energy. The locations on the switchable layer oftransmitter away from the receiver will remain at high permeability andtherefore confine the magnetic field and would not emit power.

Such an application of a magnetic field to bring the total magneticfield close to or above the saturation level can be achieved by pulsinga magnetic field from an electromagnet such as the transmitter coiland/or a separate electromagnet or coil and may be at the same time thatthe ping process described earlier occurs. Basically, throughapplication of a magnetic field created by this bias electromagnet (canbe the same as power transmitter coil or separate), the switchable layeris brought close to or over the saturation level. Then the powertransmitter coil provides an additional AC magnetic field that may bedetected through an opened magnetic aperture by any receiver coilpresent to start communication. Once this response is detected by thecharger/transmitter, then continuous power is transmitted from thecharger/transmitter and the regulation/control loop is established andpower is transmitted until the receiver sends an end of charge signal oris removed so no feedback signal is detected at the charger/transmitter.As described above, during the transfer of power, the bias magneticfield to the switchable layer may or may not be applied depending on thedesign and principle of operation.

In yet another embodiment, the receiver can contain a permanent magnetand/or electromagnet (which in some instances can be the same coil asfor the receiver coil for power transfer) that is pulsed or turned on toapply a bias field to the switchable layer to saturate it to open theaperture and start power transfer. As described above, it may bepossible to turn this bias off or remove the permanent magnet once thepower transfer has started without affecting operation.

In many applications, it may be advantageous to control the amount ofpower output to or from a receiver circuit. In one embodiment where theoutput voltage of the receiver coil to an output device or battery needsto be regulated (or adjusted) with respect to changes in the loadimpedance, an output regulator stage can be used at the output of thereceiver circuit or the input of the device or battery can be used.However, in another embodiment, it may be beneficial to take advantageof the properties of the magnetic aperture to control the power,voltage, or current delivered to the regulator. This may be achieved inany of the methods described above by controlling the amount of thecurrent to a magnetizing magnet in the receiver so that by judiciouslyadjusting the degree of saturation of the switching magnetic material,the amount of coupling to the receiver coil is adjusted and a constantor desired output voltage to the output device or battery is provided.In this way, the nonlinearity of the performance of the magneticmaterial is used to control the amount of the coupling to each receiveractively.

It must be noted that as described earlier the permeability is a tensorand the permeability of the material to magnetic field in oneorientation may be affected by a magnetic field in another orientationin anisotropic material. So, novel single or multi-layer material andfield geometries may be employed to take advantage of the magneticaperture concept. Furthermore, modeling of the AC magnetic field of thewireless charger and the switching magnetic field and the nonlinearbehavior of the ferrite layer can provide further optimization inperformance and choice of materials and geometries.

It may be further possible or desirable to switch the magnetic apertureon and keep it open in a certain location of the switchable layer. Anexample would be a charger/power supply layer where an aperture in aparticular area for power coupling is opened and kept open withoutcontinued presence of an AC or DC switching magnetic field until theuser desires to close this aperture. For these cases, it may bedesirable to use a hard magnetic switching layer such as shown in FIG.16 where the magnetic state of a region is changed by applying asufficiently large magnetic field to switch the magnetic domains in thatarea and change the permeability permanently to a state that allowstransfer of power through the aperture due to the created remanencefield continuing to saturate the material until reset by an opposingfield of value equal to the coercivity of the material or heating of thematerial over its curie temperature. An application of this may be forexample a charger/power supply table or surface or device of large areawhere at will, by application of a high magnetic field through theswitching layer with a permanent or electromagnet or a combinationthereof, a region is modified and serves essentially as a power outletfor inductive power until the user chooses to close it by application ofa reverse field or heating. This would allow intriguing possibilities inessentially creating a semi-permanent (reversible) power socket oroutlet at any location by using a magnet of proper strength and geometryto essentially punch a permanent aperture at that location to allowcoupling to the power available in the wireless charger surface. Oncethe magnetic aperture is created, placement of a device even without amagnet at that location would provide power to the device. The aperturecan be closed at will with a reversed and sufficient magnitude field orlocal heating of the region.

An analogy for the above method of regulation and control of the amountof the power transferred can be seen in a product called the SaturableReactor or Magnetic Amplifier (shown 430 in FIG. 30) where the amount ofan AC current flowing through a lamp (L) from an AC source (G) iscontrolled by the inductor T made of a ferrite core such as iron that issaturable. Another winding of the coil nearby is connected to a battery(B) or a DC power source and the current through the winding (i.e. themagnetic field and flux density incident on the core) are varied througha variable resistor (R) to change the permeability of the iron core orsaturate it to modify the inductance value along the current path to thelamp (see Wikipedia entry for Saturable Reactor). While this is a verydifferent application of modifying the permeability of a material withapplication of a magnetic field, it shows that the basic concept issolid and can be used in products.

In yet another embodiment, it may be advantageous to have a systemgeometry whereby the relative sizes of the charger and receiver coilsare reversed so that the charger coil is smaller than the receiver coiland/or the charger incorporates the switching permanent and/orelectromagnet for safety or other reasons. For example in case awireless charger for an automobile, bus, robot or other product isdeveloped such that in the case of an automobile as an example, a drivermay park a car over an area on the road or garage floor to receivercharge, it may be undesirable or impossible for the automobile (thereceiver) to include a small coil and switching magnet that would open amagnetic aperture on a larger charger surface to allow efficientcoupling. In such cases, it may be possible to design a large receivercoil and a magnetic switching layer placed below the coil (i.e. betweenthe coil and the road) such that the switching layer would cover orexceed the area of the receiver coil. A smaller coil in or near theground/road/floor and an in the case of MA configuration, appropriatepermanent or electromagnet of appropriate size placed in the charger (onthe ground or floor) and would open a magnetic aperture in the switchinglayer of the receiver (in the car) to allow optimum coupling of thecharger and receiver coil when the automobile receiver coil and itsswitching layer is placed on the charger coil. In this configuration 440shown in FIG. 31, the charger switching magnet and optional chargerand/or receiver shielding layers are shown. In addition, the receivermay include a surface or outer layer, skin, body, etc. that may belocated between the ferrite, magnetic material or switching layer andthe charger surface. It must be noted that any embodiments described inthis document may be combined with the geometry of FIG. 31 to be usedfor cases where larger receiver coils and smaller charger coils may beused.

In a Magnetic Coupling (MC) embodiment of this geometry, the switchingmagnet and the optional switching magnet shown in FIG. 30 would not berequired.

In yet another embodiment to allow for charging an automobile or othervehicle or movable system such as a robot, etc., the coil on thestationary part (the road or the floor) or alternately the moving part(car, robot, etc.), can be made to be much longer and/or wider than theother coil to avoid the need for precise alignment. For example acharger coil on a floor or road can be in a rectangular or oval shapewhile the receiver coil in a car is circular and placed at any locationat the bottom center line of the car. In this way, the driver does nothave to precisely align the coils in the front and back direction to usethe charger. Similarly, different cars with the receiver coils placed atdifferent locations in the car can use the same charger.

Another method for achieving the goal of modifying the permeability ofthe switchable layer locally is to use the Curie temperature property ofa ferromagnet to alter its properties. Curie temperature or point is thetemperature at which a ferromagnetic or a ferrimagnetic material becomesparamagnetic upon heating. An iron magnet for example will lose itsmagnetism if heated above the Curie temperature and the effect isreversible. In optical recording, a laser light is focused on a datatrack to be written and the local temperature is raised over the Curietemperature. At the same time, a nearby coil will create an alternatingmagnetic field that mimics the data to be recorded. As the locationunder the laser beam is heated, the data is erased and the magnetizationis changed to the direction dictated by the applied external magneticfield. Once the laser beam is passed and the material cools, thatmodified location of material is fixed and the up/down magnetization isfrozen into the material to be stored and/or read back through magnetooptic detection of polarization change of an incident optical beam whenthe track is read back.

Nickel (Curie Temperature of 358° C.) and Iron (Curie Temperature of770° C.) or alloys of these materials are often used for this type ofrecording application. Lower Curie temperature ferromagnetic materialcan also be designed. As an example, the ferrite material used with highefficiency in the MA section above has a Curie temperature of 200° C.,Similarly, in the wireless power case described above, in oneembodiment, the receiver may locally heat a switchable layer opticallyor through resistive heating or a combination of the above to locallymodify the permeability and affect the amount of power transfer byopening a magnetic aperture while leaving the rest of the area of aswitchable layer unmodified to shield the transmitter coil magneticallyand reduce or eliminate emission.

Use of the Curie temperature effect and the magnetic saturation may becombined or used individually to design an optimized system as describedabove and to achieve best performance.

In another implementation for use in other applications, a ferromagneticlayer that has an EM field incident on it, may be modified in a one or 2dimensional manner as desired by placing pixels or arrays ofelectromagnets such as printed or assembled coils or alike along thefront and/or back or inside such a material. This may be combined withfield from one or more permanent magnets to bias the operation near thesaturation level. By locally activating the electromagnets, the localpermeability may be modified affecting the phase and amplitudetransmission and/or reflection properties of the EM wave at thatlocation.

While the above descriptions relate to modifying the amount and locationof power transmitted from a 2 dimensional wireless power system, theconcept can be used for modulating the transmitted and/or reflectedamplitude and/or phase of any electromagnetic and/or magnetic wave byusing a ferromagnetic layer. In a general sense, the description aboveis for the first time describing the concept of locally modifying theshielding and/or magnetic properties of a magnetic or ferromagneticlayer by application of one or more or a combination of permanent and/orelectromagnets and/or temperature to modify the magnitude and/or phaseof the reflected and/or transmitted electromagnetic or magnetic field atany location in the 2 dimensional space while passing through orreflecting from such a layer. Beyond wireless power, this may haveapplications in shielding or modulating the amplitude and/or phase of a2 dimensional electromagnetic or magnetic wave spatially. Applicationsmay include phased array radar, beam steering, EM cloaking, beam formingand shaping, etc.

One advantage of use of a magnetic aperture (MC) or magnetic coupling(MC) in a wireless power transmission system is that the amount of powertransferred and characteristics of the system may be determined by thesize of the receiver coil and associated magnetic including magnet ifany. So using a large transmitter coil, a designer may have flexibilityin powering a variety of receivers and associated devices/power levelswith the same transmitter coil. For example, a large receiver coil andassociated possible magnet or electromagnet or heater (for curietemperature operation), may be used for providing relatively large powerand to charge or power a laptop, power tool, or lamp, etc. while asmaller coil and magnet (in case of MA) may be used to power or charge amobile phone or Bluetooth headset. Such flexibility is very advantageousin many applications.

In a loosely coupled system, two or more receivers may be placed on andpowered or charged from one transmitter coil simultaneously due to thesize mismatch. The inventors have tested placement of two or morereceivers on the both types of charger surface (MC and MA) describedhere, and shown that in either configuration multiple receivers can bepowered simultaneously while detecting no or low emission from any otherarea on the surface. This allows for the development of charger systemswhere multiple (2 or more) receivers can be powered or chargedsimultaneously. In accordance with various embodiments described here,the receivers can provide different power levels and/or voltages todifferent products or parts or be operating with different protocols oroperating frequencies. The sizes of the receiver coil, number of turnsof the receiver coil, the regulation mechanism and overall system designcan also be optimized to address a particular design requirement. Thisallows for the development of power surfaces with little or no powerdissipation or emission (since the system is not in resonance and in lowcurrent draw state without a receiver). The same surface can also poweror charge multiple devices including lamps, kitchen appliances, laptops,keyboards, computer mice, mobile phones, power tools, batteries, etc. asneeded by simple placement on or near the surface. Experimentally, theinventors have found that, depending on the degree of resonance that canbe adjusted by adjusting the Q of the system, the receiver can also besome distance (up to several cm) from the charger surface and receivepower. This also allows placement of the charger pad under a table orsurface if necessary. In such a system, depending on configuration,power transferred to each receiver may or may not be individuallyadjusted since any adjustment would affect operation and power receivedat all receivers. Methods for adjustment of power to each receiver mayinclude serially or alternate powering of each receiver whereby thereceiver disconnects its coil for a period allowing only one or a numberof receivers to receive power or regulation of power at the receiver ora combination of the above. In this Time Division Multiplexed (TDM)arrangement, each receiver is powered for a period of time by having itsreceiver coil connected to the receiver circuit and output load, beforedisconnecting that receiver and moving on to the next receiver. Theadvantage of this system is that during each power delivery time slot toeach receiver, a one to one power delivery and communication connectioncan be established and the output voltage, current, and/or power can becontrolled by the charger/power supply through communication andfeedback during this period before moving on to the next receiver, etc.The disadvantage of this architecture is that each receiver onlyreceives power during some period of time instead of continuously. Sucha condition may not be acceptable for some applications. In general, itwould be desirable for the time slots for powering each receiver to beshort enough so that the receiver or charging circuit in the device orbattery does not notice the connection and disconnection of receivedpower.

Another problem that has been noted in use of wireless power systems forcharging and powering of devices or batteries has been that in case ametal object is placed between the receiver coil and the charger coil,the AC charging magnetic field may cause unwanted heating and safetyissues. It is therefore desirable to detect such a presence and takecorrective action. Corrective action may include termination ofcharging, reduction of power, notifying the user by an error message ora combination thereof. Several methods for detection of such foreignmetal objects are possible. In a simple method, a thermal detector orthermistor in the charger and/or receiver detects an abnormaltemperature rise in the charger or receiver coil area and correctiveaction is taken. Another method may be to measure or estimate the powerdelivered to a device or battery at any given moment and comparing it tothe delivered power to the charger/transmitter, ensure that safeoperation is being conducted. This can for example be done by thereceiver reporting the power delivered values to the charger and thecharger comparing it to the power or current it is delivering to thecharger coil and taking corrective action if anomalies are observed.However, an advantage of the magnetic aperture system described here isthat the magnetic aperture created depends on the application andsensing of the magnetic switching AC or DC field from the receiver tosaturate the magnetic layer. Presence of metals in between the chargerand receiver coils, may reduce or eliminate the magnetic aperture andtherefore automatically reduce or shut off the power transfer. Thedegree of this effect would depend on the type, composition, and size ofthe metal object involved but with appropriate design of the charger andreceiver coil, the switching magnet and the switching material wouldenable design of products that may inherently be safer in this respect.In addition, this technique may be combined with the other techniquesdescribed above to provide further safety. In practice, the inventorshave tested this by placing a large magnetic metal sheet of StainlessSteel in between the charger surface and a receiver coil and itsswitching magnet. While the amount and efficiency of the power transferwas affected, wireless power transfer continued without or with minimaleddy current heating of the sheet. This occurs because the StainlessSteel shields the magnetic switching layer in the charger from theswitching magnetic field of the ring magnet in the receiver. Thus themagnetic aperture is only partially (area wise) opened only in the areasof overlap of the receiver coil and the charger surface where the metalsheet is not. In this way, power transfer can continue in this area andsince the other parts of the metal sheet are on top of the magneticlayer that is not opened, it does not receive any power from the chargerand thus no or minimal eddy current and heating is generated. A ringmagnet was used in this case but the results are not limited to thisgeometry and are general with respect to a variety of magnets andgeometries. Similar results may be obtained in the MC configuration.

In some applications, it may be desirable to be able to charge wirelesspower receivers at a distance from the charger surface or electronics.Examples for consumer application include a wireless charger that ismounted or attached under a desk or table to charge devices placed ontop. Another case may be charging of a battery powered, electricautomobile or vehicle. Depending on the charger and receiver coil sizeand operating frequency, Q of the cavity, etc. the operating distancevaries. The inventors have found that in a ‘traditional’ loosely coupledsystem (i.e. without the magnetic layer) such as described above (with18×18 cm charger coil and 35 mm diameter receiver coil) coils can beseparated to distances of several cm while significant power istransmitted. The inventors have obtained power transfer of over 20 Winto a single coil at up to distances of 3 or 4 cm. However the systemefficiency may be reduced to 50% or lower for these distances. Thesegaps are sufficient for most of the consumer electronics applicationsenvisioned.

Similarly with a magnetic layer system in MC or MA configuration asdescribed above, the distance between the receiver and the charger canbe increased while continuing to receive power. However, two parametershave to be kept in mind. One is the Q of the resonator and/or thedistance where the electromagnetic field exists away from the chargersurface (which is governed by the frequency of operation, coil size,magnetic material properties, pattern, etc.) and the other is the fieldpattern from the switching permanent or electromagnet that is requiredto open the magnetic aperture in the MA configuration. This switchingfield should be of sufficient dimension, direction, and shape toeffectively affect the switching magnetic layer and modify theproperties to open an aperture and allow efficient coupling. It wasexperimentally observed that in a system similar to the loosely coupledsystem described in the last paragraph but with a switching layercovering the charger coil and a ring magnet similar to FIG. 22 in thereceiver, efficient (up to ˜50% efficiency) power transfer at up toabout 2 cm vertical coil to coil gap can be obtained. Somewhat lessefficiency but larger operating distances can be obtained in the MCgeometry without the switching magnet and with a different andappropriate receiver coil. It must be noted that even with a large gapbetween the charger and the receiver, the areas around the receiver donot contain significant Electromagnetic emission as tested by placingmetal parts in this area and not observing much change in powertransferred or pulled from the DC supply providing power to the charger.The reason for the presence of the coupling is the enhancement achievedby the resonant circuit (in the MC configuration) combined by the openaperture created in the MA configuration. As the gap is increased fromaround 2 cm, power transfer drops rapidly in the MA configuration. Thismay be due to the field of the switching magnet reducing and not openingthe magnetic aperture completely. Proper optimization of the design andtype of magnet, coils, switching layer or use of multiple layerswitching layers could significantly improve this.

To enable the system to operate at larger gaps, several embodiments arepossible. In one embodiment, the magnetic layer (ferrite or othermaterial) is separated from the charger coil such that a gap between thecharger coil and the switching layer exists. This gap can be severalcentimeters. Since the magnetic or switching layer (in the MAconfiguration) is a high permeability material, it is quite an effectivematerial to draw the emitted magnetic field from the charger coil intoitself. Therefore, even at large distances, the layer acts as aboost/repeater, or flux reservoir layer and good coupling into thislayer exists. This power can be coupled into a receiver placed on or ata distance from this layer. In the MA configuration, when a receiverwith a switching magnet is placed on or over the top surface of thislayer, the magnet would switch the switching layer and receive powerefficiently. Therefore, large gaps between the charger coil and areceiver can be obtained. Experimentally, a planar magnetic layer offerrite material described above was placed at a distance of 3 cm awayfrom the top surface of a charger coil of 18×18 cm as described above.An MA receiver (as described above) placed on the magnetic layer orwithin 2 cm of the layer would receive powers in excess of 20 W atefficiencies comparable to the case with the magnetic layer adjacent tothe charger coil. In this case the magnetic layer essentially acts as areservoir of AC power magnetic field away from the charger that isavailable for the receiver to tap into at a magnetic aperture locationto draw power from. Similar results can be obtained in the MC geometrywith the appropriate receiver and no switching magnet. Such embodimentsare attractive in the case of a desk charger where the charger coil andthe associated electronics can be placed or attached to the underside ofa table or desk top or the console of a car and the size and bulk ofthis part is hidden while a thin magnetic layer (can be a thin solid,flexible ferromagnetic, ferrite or other material) is placed on top ofthe desk or away from the charger coil to indicate the region ofoperation or carry a logo or be decorative or interchangeable, etc. Thisrepeater layer can be a 0.5 mm or thinner layer and can be flexible orcurved etc. as necessary and while being decorative or used to notifythe user about where to place a device for charging/power, can serve theimportant shielding, guiding, and/or switching functions. Any of thematerials described earlier can be used for this. Optionally, thecharger coil and/or electronics can also have a shield on the oppositeside to prevent emissions from the opposite side of the charger. Thethin shield/repeater layer on top of the desk/table/console can alsoprovide additional functionality or information to the user. For examplethe layer can be combined with a wireless power and/or data receiverand/or electronics and display relevant information to the user.Examples include start of charge, status of devices being charged,errors, etc. through use of displays, LEDs, electroluminescent displays,parts, etc. Such a display or layer may be as thin as 0.5 mm or thinnerand can provide a multitude of functions.

In another embodiment, a wireless charger/power supply can be placedunder a table top and a display or tablet built in or attached to thetop and powered from below. The display and/or tablet can also include aportion or surface for charging or powering other devices on it orseparate from it. The tablet alternatively may display the chargerstatus or information about devices being charged/powered.

In yet another embodiment, a wireless charger surface with or without amagnetic top layer (i.e. MC, MA, tightly or loosely coupled or any otherconfiguration) may be covered totally or partially with anelectroluminescent (EL) and/or LCD or other display. These structurescomprise several layers that may be constructed of metal and/orsemiconductor and/or plastic and/or glass but may be as thin as 0.1 mmto several mm. Even though the structures would contain metal layers forapplying a field for the device to operate, these layers are extremelythin (several nm to microns) and allow the magnetic field of a chargerto pass through. It has been found that the surface of a MA or MC ortightly or loosely coupled charger can be totally or partially coveredby an operating EL display while the charger operates normally with nosignificant reduction in power transferred or efficiency. It is alsopossible to construct the charger and/or receiver into or on anelectronic display or screen. The charger and/or receiver coil andcircuits may even be constructed of printed circuit or plastic materialused to manufacture the display to save processing steps and complexity.

In accordance with an embodiment, the charger is a stand-alonedevice/pad or other shape combining a display and chargingfunctionality. The display can provide information useful for the userof the charger or can be a fully functional display for information suchas a tablet, netbook or computer or table top computer display. Forexample a tablet may incorporate a wireless charger on its top displaysurface. By placing a mobile phone or camera on the display of thetablet, charging may commence and additionally, other functions maystart. For example data, images, music, etc. may be transferred from oneto another.

In the case of a desk wireless charger described above where the chargercircuit is placed under the desk and a magnetic layer is placed on topas a magnetic boost or reservoir plus shield layer, it may be beneficialto provide LEDs, a charge indicator or other information to the user. Inthis case, according to an embodiment, all or a portion of theboost/magnetic layer is covered or integrated with an EL, LED or otherlayer and powered by the applied power from below and a small circuit toprovide indicator LEDs, charge percentage, or other info or a fullfeature display to the user. As an option, in public area uses orkiosks, advertisement or other info can be provided to the user whiledevices are charged or powered on or near the display. The display andthe charger layer can each be less than 0.5 mm thick or similar and canalso be flexible or rollable and/or laminated or itselfhermetic/impervious to environments and also allow accommodating acontour or curve or be rolled and unrolled like a placemat. Manyapplications and embodiments of this are possible and the possibility ofa wirelessly powered display and/or charger can be used in manyapplications.

In various other applications, including U.S. patent application Ser.Nos. 12/400,703, 12/210,200, 11/408,793, 11/654,883, 12/543,235,12/250,015, 12/211,706, 12/427,318, 12/756,755, 12/618,555, 12/510,123,12/323,479, 12/479,581, 12/505,353, 12/351,845, 12/189,720, 12/394,033,12/547,200, 12/040,783; and U.S. Pat. Nos. 7,741,734 and 7,825,543,wireless power systems for operation with large distance between thecharger and receiver have been described. These systems generallyoperate as loosely coupled systems but have also been called magneticresonant systems. However, the inventors recognize and have describedthe safety and regulatory issues arising from the large electromagneticemissions present in such systems. Meeting regulatory and human safetystandards are challenging and may be only achieved for limited poweroutputs and in certain frequencies of operation intended forunrestricted power output. Some of the embodiments of the systemsdescribed here attempt to overcome such restrictions by limiting oreliminating the Electromagnetic emission and exposure from wirelesspower systems by use of a magnetic aperture.

To achieve the large operating distance possible by systems usingloosely coupled or magnetic resonance technology whereby the couplingcoefficient is small, previous investigators have found it necessary orpreferable to operate the systems at high Q values often exceeding 100or 1000. To overcome parasitic losses in a coil and driver system,previous investigators have also found it preferable to utilize 2 coilsfor the charger and 2 for the receiver. This system 450 is shown in FIG.32. The charger/driver electronics in the first coil is powered by thetransmitter/charger drive electronics and produces an electromagneticwave that couples to a charger resonant antenna placed nearby through acoil L1. This antenna is the one that actually transmits power over adistance and comprises an LC circuit formed by a low resistance wire orcoil loop (L_(c)) and a capacitor (C_(c)). Due to high Q's encountered,the voltages generated may exceed 1000's of V so appropriate highvoltage capacitors may be needed. The receiver (used in or on orattached to a mobile or electronic device or battery) comprises areceiver resonant coil (L_(r)) and a capacitor (C_(r)). The receiverresonant antenna may have similar construction and/or Q or moretypically be of smaller dimensions and/or Q of the charger. The wirelesspower is transmitted over a distance between the 2 resonant antennasdescribed. This received power is then in turn coupled to a receivercircuit through a coil L2. The power is then rectified and smoothed andconnected to a load. An optional regulator or power switch may also beincluded in the receiver. This description describes a simplified systemwith no communication and/or microcontroller control. In practice, theseelements may be needed as described in earlier systems.

In loosely coupled systems as described here, it may be possible toincrease the distance between the charger and receiver coilsadditionally by adding passive resonant antenna elements to act asrepeaters. This configuration 460 is shown in FIG. 33 where one or morerepeaters are inserted between the charger and receiver resonantantennas.

While some of the systems described here use 2 coils for the charger and2 for the receiver, systems with single charger coil and single receivercoil or 2 coils on either charger or receiver are also possible forloosely coupled/magnetic resonance systems as described in earliersections. In general, due to potentially lower Q factors, these mayoperate at lower charger/receiver distances. The descriptions here areattempting to capture the various systems possible in the most generalsense and are not meant to limit the description of the embodimentspossible.

One of the key observations in this system is that the magnetic fieldgenerated between the 2 resonant antennas (or resonant antennas andrepeater antennas) is quite large and enhanced owing to the resonanceand the high Q used. This would in many cases cause unnecessaryemissions, human exposure, and/or eddy current heating and interactionwith metals nearby.

In accordance with an embodiment and building on the concepts of MC andMA configurations described above and shown 470 in FIG. 34, a layercomprising magnetic or ferrite or other material is added to the chargerto limit the emission from the charger into space. The receiver maycontain a permanent magnet or electromagnet (in the MA configuration) tolocally modify the switching layer and create a magnetic aperture forlocalized and efficient transfer of power to the receiver. Theefficiency of such a system would exceed the regular loosely coupledsystem due to the elimination or reduction of loss of power tosurrounding areas and the extraneous unwanted electromagnetic emissionswould be greatly reduced as described earlier. It must be kept in mindthat a variety of materials, parameters, and geometries for themagnetic/switching layer, magnet, coil, rectification, regulation, oradditional elements for communication, control, detection of foreignobjects, thermistors, etc. are possible as described here and FIG. 34 isgreatly simplified to more clearly illustrate the basic elements of thesystem. It must also be noted that as described earlier, themagnetic/switching layer may be placed at a distance from the chargerresonant coil and similarly the receiver magnet may be at a distancefrom the magnetic/switching layer and/or the receiver resonant coil. Inaddition, as described earlier, the magnetic/switching layer may ineffect act as a reservoir of power due to its high permeability and drawthe power away from the charger coil in a similar manner as a resonantantenna or a repeater antenna. Thus several geometries with a large gapbetween the charger coil L1 and the charger resonant antenna with themagnetic/switching layer close to the charger resonant antenna or closergap between the charger coil L1 and the charger resonant antenna and alarger gap between the charger resonant antenna and themagnetic/switching layer or a combination of the above is possible tocreate a larger gap between the charger and the charger surface or thereceiver. Similarly many variations in placement of the receiverswitching magnet or electromagnet exist. In addition, one or moremagnetic/switching layers and optionally (in case of use of MA) magnetsmay be placed at one or more locations of a system such as shown in FIG.34 to funnel or better control the direction and flow of the power asshown in FIG. 35 to increase efficiency and reduce unwanted emissions.

In the geometry 480, 490 of FIG. 35 and FIG. 36 respectively, one ormore repeater antennas and one or more magnetic/switching layers andoptionally (in case of use of MA) magnets and/or electromagnets are usedto extend the range between the charger and receiver while controllingthe emissions. It must be noted that as described above,magnetic/switching layers and/or repeaters and/or resonant antennas maybe used in a number of combinations and placements to extend the rangeas appropriate for any application.

As an example of the embodiments described above, a charger may beplaced below a table or console and the resonant coil and amagnetic/switching layer placed on top of a table in a thin layer to beclose to receivers embedded or attached to devices and/or batteries. Inanother geometry, the charger and the charger resonant coil may be undera table or a long distance away and a repeater can be placed below or ontop of table with a magnetic/switching layer directly or with somedistance on top of it to for the device to be placed on top of. Manydifferent geometries are possible with the combination of approachesdescribed here to provide efficient power transfer to one or morereceivers while keeping extraneous unwanted emissions to a low level.

It must be noted that in these embodiments a larger charger resonantcoil and smaller receiver coils is described. However, as describedearlier, the opposite may be preferable in some situations and themagnetic/switching layer may be placed closer to the receiver and anyused switching magnet may be close or part of the charger.

In addition, while the MA or MC configuration and use of a possibleswitching magnet is described here, any of the combinations of heat, dc,and or AC magnetic fields and/or use of hard magnets or self switchingdue to high AC magnetic fields, etc. can be used to achieve desiredperformance and characteristics. In addition, any magnet if used canhave a variety of shapes and geometries as described earlier.

Many of these combinations of technologies may be advantageous tosystems where high power and large charger/receiver gaps are desiredsuch as charging electric vehicles, etc.

In accordance with an embodiment, the charger coil and/or themagnetic/switching layer is curved or folded to form a non planar orenclosed surface. Examples include a charger bowl or cup where mobiledevices can be placed to be charged. Such a cup may be advantageous inan automobile cup holder as an example to allow the user to place aphone into the cup for charging. The charger coil can be constructedfrom Litz wire and/or flexible PCB material to cover the entire or aportion of the surface of the cup. This can be covered by an appropriatemagnetic/switching layer and when a mobile device or receiver with theappropriate magnet (in case of MA configuration) is placed inside thecup, it can switch the appropriate location on the cup to allow flow ofpower and charging of the device without affecting nearby parts orextraneous emissions. In an MC configuration, no switching magnet wouldbe necessary.

As an alternative, the charger coil may be flat and the magnetic orswitching layer is formed in the shape of a cup, cup holder cylinder orother bowl, etc. or laminated with solid or flexible material such asflexible magnetic material or ferrite as shown 500 in FIG. 37. Forexample, in an embodiment such as shown in FIG. 37, the wireless chargermay be in the shape of a cup for placement of mobile devices inside toreceive charge/power. The charger can be powered with the chargercircuit integrated into the cup or cup holder or inductively throughintegration of a receiver and charger drive circuit into the cup or cupholder or directly simply by having the charger circuit and coil at thebottom as shown in FIG. 37. When inductively powered, the bottom of thecup or cup holder may be from the same magnetic material or othermaterial to guide the flux to the walls and may even contain a repeaterantenna as described earlier to allow large gap between the charger andthe cup. The charger coil may be at the bottom or at a distance from thecup and flat or curved and the flux is guided up the sides with aferrite material shaped like a cylinder or coated or laminated withflexible ferrite or other magnetic layer to allow a device withappropriate receiver and/or switching magnet (in the case of MAconfiguration) to be charged when placed inside. Additional shieldingmaterial may be placed on the outer surface of the charger to shield thecharger radiation externally. Many other shapes and configurations arepossible with the technology described here.

Alternately, as described above and shown 510 in FIG. 38, the chargercoil can also be wrapped around the vertical cylinder body while theinside of the cup uses the magnetic solid material, layer or laminatedfilm. The charger coil is only partially shown. The coil would wraparound the entire or the desired active part of the surface of thecylinder or cup or cup holder and comprise one or more coils. Manygeometries of coil and construction by wire, PCB, Litz wire or acombination are possible. In this case as described above, the chargercoil may be powered directly by a charger circuit powered by wired poweror a charger circuit that is itself powered inductively whereby awireless receiver is integrated into the cup or cup holder and ispowered by a wireless charger base. The ability to separate the chargercup/cup holder from the charger body/surface (base) as shown in FIG. 37may be advantageous and provide flexibility in some circumstances.

In all of the embodiments described here, the electronics in the chargerand receiver may be implemented using discreet electronics components orApplication Specific Integrated Circuits (ASICs) that would combine avariety of the functions and electronics components into one or severalcomponents and enable further integration and reduction in cost andfootprint.

Overall, many geometries or architectures for wireless power systems arepossible. In network systems and internet, terminology for the methodsfor transfer of information from a source to one or many differentrecipients has been developed. A similar terminology is used here toconsider powering one or multiple receivers. For cases where thereceiver must be placed on or near a fixed position, systems such astightly coupled systems are used. The architectures below can useloosely, or tightly coupled systems or use a ferromagnetic layer andcreation of a magnetic aperture as described above or a combination ofthe above to achieve positioning freedom. This description is thus moregeneral and attempts to illustrate the different control andcommunication methods that can be used. In one view, the wireless powersystem can be described as a power transmission system (wireless chargerand receiver circuitry) and systems for control, regulation, safety andother features necessary.

Having dealt extensively above with the power transmission system andmethods of power delivery in tightly, loosely, and magnetic coupling andmagnetic aperture systems, methods will be described herein for thecontrol, regulation, and safety of the system (control system). Toimplement the systems with desired characteristics, a close interactionand appropriate design between the power transmission system design andthe control system design is necessary.

FIG. 39 shows several possible architectures 520 where the chargercircuit comprises sub circuits or units whereby each sub-unit isresponsible for powering or charging and/or communicating with one powerreceiver. The arrows in FIG. 39 show the direction of the power transferto the device to be charged. However, the direction for thecommunication and/or control can be in the same direction, the oppositedirection, or bidirectional or no communication and/or control betweenthe charger and receiver may exist. In addition, the communicationand/or control can be through the coils, by load modulation, separatecommunication coil or coils, RF or optical path, etc. or a combinationof such methods. As described above, existing protocols such asBluetooth, WiFi, NFC, RFID, Zigbee, WiGig, Wireless USB, or protocolssuch as that provided by the Wireless Power Consortium (WPC), developedfor wireless power, or a combination of the above and/or new protocolsor proprietary communication mechanisms can be used. As described above,it is also possible to develop systems whereby there is no communicationbetween the charger and receiver and any regulation or end of chargetermination and/or shut off due to unexpected events occurs in thereceiver.

A simple example of such one to one architectures is a multi-chargertightly coupled system where multiple identical or similar chargercircuits are replicated several times in a charger and connected tosimilar coils to allow powering or charging several receiverssimultaneously and mostly independently. a) In this architecture, acharger can only support one protocol and the Charger circuit iscomposed of multiple sub-units where each sub-unit powers and/orcommunicates with one receiver. The charger coil or active area isdefined and in tightly coupled systems each receiver coil must be placedon or near a charger coil to receive power/charge. Little positioningflexibility exists. An example of such architecture is a multi-chargertightly coupled system where multiple identical or similar chargercircuits are replicated several times in a charger part or product andconnected to similar coils to allow powering or charging severalreceivers simultaneously and mostly independently. b) In thisarchitecture, the positioning freedom is limited as in a) but the systemis designed with its hardware and/or firmware so that each charginglocation is capable of operating in one or more communication and/orpower protocols, providing different voltages, and/or power levels andthus providing more flexibility. Some of the ways to achieve thismulti-protocol flexibility or achieving different voltages and/or powerlevels are described earlier. c) In this architecture, the chargersurface may be divided into sections where a receiver can be placedanywhere or with a larger degree of positioning freedom and be poweredor charged. This architecture only supports one protocol, voltage and/orpower level in each of the charger sections. An example may be amagnetic resonant (loosely coupled) or magnetic aperture or acombination of these systems where the charger comprises several similarcoils and/or driver and/or communication circuits and they operatemostly independently to power or charge multiple devices simultaneously.Alternately, each region may provide positioning freedom with tightlycoupled technologies such as coil arrays or a moving coil as describedearlier. d) This architecture is similar to (c) but it may supportmultiple protocols, voltages and/or power levels in each of the chargersections. This can be achieved by some of the techniques describedearlier.

As an example of FIG. 39(d), a power transmitter/charger/power supplymay comprise a number of transmitter coils and associated control andcommunication circuits operating in tandem or independently. Thecharger/power supply/transmitter surface may thus be divided (andidentified to the user) to contain independent sections so that the usermay place one receiver on or near each section of the charger/powersupply/transmitter to be powered and/or regulated by its associatedelectronics. Each section may operate as a position independentcharger/power supply through use of the techniques and geometriesdescribed here so that the user may place the receiver in any positionon the charger/power supply/transmitter for operation. Another device tobe powered and/or charged may be placed in another section and similarlyoperate in a position independent manner in that section.

FIG. 40 shows a geometry 530 where multiple transmitter coils coverdifferent areas of a multi-charger/power supply. Within each section,devices with different power rating and/or coil size and/or using thesame or different protocols may receive the appropriate voltage andpower required. Loosely coupled systems or tightly coupled position freesystems within each section can be used to achieve positioning freedom.Although support of multiple protocols or power or voltage levels wouldrequire that any system employed in each section be flexible andadaptable in these regards.

Alternatively, or in addition, as shown 540 in FIG. 41, as describedearlier, use of a magnetic layer and creation of magnetic coupling or amagnetic aperture for coupling of power to receivers can providebenefits in efficiency, positioning flexibility and/or lower unwantedelectromagnetic emission. Each section has an independent power driverand/or communication sub unit system to operate with the receivernearby. In this way, control and regulation of individual devices andposition independence can both be achieved. However, in protocolswhereby the receiver signals to the charger about amount of power tosend and takes control of the operation of the charger, placement ofmore than one device in each section may not be permitted since theregulation and control system operates by communication between thereceiver and charger in each section and adjustment of thepower/operation in that section. In practice, this may not be asignificant disadvantage to the user.

One of the interesting aspects of the architecture in FIG. 40 or FIG. 41is that even if position free technologies such as loosely coupledchargers or magnetic coupling or magnetic aperture are used in thecharger, it may be designed to be backwardly compatible with tightlycoupled receivers and/or protocols. As described earlier, tightlycoupled systems such as those that use the Wireless Power System (WPC)protocols, are in general designed to have communication between onecharger sub unit and a single receiver system and in their basic formdesigned to establish this through communication through the coilalthough other methods and paths of communication can also be supportedby the architecture in FIG. 40 or FIG. 41. By appropriate design of thecharger or transmitter coil, the value of the resonant capacitor, thecommunication system in the charger, etc. a position free charger thatcan detect and power receivers designed for tightly coupled systems canbe designed. To achieve this, the resonant conditions of the positionfree system may need to be tuned to the right frequency of operation andthe right protocol used to understand and act on the communicationmessages from the receiver. An advantage of this type of approach may bethat by using a larger coil and more flexibility, multiple output powersor voltage levels may be supported in different types of receivers thusobviating the need for multiple coils or circuits in the charger topower different types of receivers. Additionally, differentcommunication or power protocols may also be supported to provide moreflexibility.

FIG. 42 shows a mobile device 550 such as a mobile phone with a receivercoil and receiver circuit integrated into the back cover or batterydoor. The receiver circuit including rectifier, control, communication,etc. may be placed on this door and the power connection to the devicemade through pins or alike to the rest of the device. The main devicemay also contain a charger IC and or means of allowing wiredpower/charging for the device and an automatic or user controlled methodfor switching between wired and wireless charging. To use the wirelesspower receiver on a position free charger system using magneticaperture, a switching magnet is also required to locally saturate theferromagnetic switching layer. This is shown as a ring magnet with a cut(for reducing or eliminating eddy currents) here but can have differentshapes and size as described earlier. Similar components may also beused in after—market or optional device cases, battery doors, skins orbatteries to allow a non-wireless chargeable device to be enabled forwireless charging. In such cases, battery door or skins or batteries,the receiver coil and the circuitry may be included in the case, batterydoor, skin, or battery and connected to the device power input throughthe power connector of the device or pre-existing power connections onthe back or side of the device, etc. Alternatively, the coil and thereceiver may be integrated into the original or after-market battery ofthe device and directly charge the battery. In these cases, the receivermay also contain battery charging ICs and protection and or thermalcircuits and circuits for detection of wired charging current into thebattery and battery ID or other circuitry. In the MA configuration, forthe receiver with a position free charger as described earlier with aswitching layer, a method for switching the layer is needed. This can bea magnet, electromagnet, or a combination thereof as described abovethat are added or adhered to the front, back or around the receiver coilduring manufacture or afterwards by the user or the product manufactureror seller to create the appropriate magnetic aperture on the chargerswitching layer when the receiver is placed on the charger. For example,for a phone case or skin where the coil is in the case, the magnet mayalso be integrated inside the case by the manufacturer. In addition, theinventors have found that tightly coupled receivers such as thoseintegrated into after-market cases or skins to work with tightly coupledprotocols such as the wireless power consortium (WPC) can operate onposition free magnetic aperture charger surfaces if one or more magnetsof appropriate polarity, size, strength and material can be attached tothe outside surface of the case facing the charger thus enabling astandard tightly coupled receiver to also operate on a position freecharger surface providing a high degree of flexibility. It must be notedthat such a receiver will continue to work on the original tightlycoupled (fixed position) charger for which it was designed for since theattachment of the magnet to the outside has no effect on itsperformance.

In one example, the inventors attached an axially magnetized 1.5 mmthick Nd ring magnet similar to FIG. 22, aligned to be centered aroundthe coil in the protective case. to the outside of a Wireless PowerConsortium (WPC)-compatible device (such as that commercially sold by,e.g. Energizer for use with, e.g. Apple iPhones and other mobiledevices), and tested this tightly coupled receiver on a position freemagnetic aperture system with 18×18 cm surface area comprising a coilwith pattern similar to FIG. 12 and covered by a layer of 0.5 thick MnZnmaterial of appropriate permeability and switching magnetic field value.Operating the charger at the appropriate frequency of around 175 kHz,the charger can power the receiver and communication and regulation ofpower through the coil (through the opened magnetic aperture) can beachieved allowing position free, regulated power charging. The chargercan fully implement the appropriate protocol and operate similar to afixed position charger while retaining the flexibility in placement ofthe receiver. In addition, the receiver and case continue to functionnormally when used with a standard WPC-compatible charger. SinceWPC-compatible systems contain an alignment disk magnet ofpre-determined size, shape, and strength at the center of the chargercoil (and a magnetic attractor at the center of the receiver coil foralignment), care must be taken in the polarity of the ring magnetattached to the case so that the case receiver would continue to alignand center on the charger and not repel each other. Since a ring magnetof larger diameter is used here, addition of this magnet in factenhances and adds in the centering by providing further tactile feedbackand pull force to the user when the receiver is placed on or near thecharger magnet of a smaller diameter in the charger thus enhancing thecentering process with the standard WPC-compatible charger. On aposition-free charger with a switching layer, the polarity (N-Sorientation) of the magnet is not important for the switching layersince it responds to the magnitude of the total field (DC/AC switchingmagnetic field+AC wireless power magnetic field) so the choice ofpolarity is not important. This however, does become important if a biasDC magnetic field by a permanent or electromagnet is added to thecharger as described earlier to lower the receiver magnetic fieldnecessary to switch the layer.

Similarly, a magnet or magnets can be attached or added to the inside,backside or on the top surface of the cases, battery doors, skins,devices, batteries or back sides or batteries at the right location withrespect to the receiver coil to enable a regular tightly coupledreceiver to operate in a position free magnetic aperture system as well.

In accordance with an embodiment, such an addition or attachment cantherefore be used to enhance the usefulness of wireless power receiversintegrated into various products such as cases, skins, devices, doors,back plates, or batteries by adding or attaching one or more appropriatemagnets of the appropriate size, strength, and shape to enable thereceiver to operate with a position free magnetic aperture charger. Thismay take the shape of a thin, light weight sticker or adhesive part orlogo that is adhered by the user or in the manufacturing process to theright location on or in the case, skin, battery door, back plate, orbattery to enable this additional functionality. Considering that themagnet may be a very thin and/or flexible magnet, this can be also madeto be quite inconspicuous and to add very little to the thickness of thedevice and/or receiver. As described earlier, a variety of types ofmagnets and even multi-pole magnets may be used. In conditions such ascharging inside automobiles, airplanes or other vehicles, trains orboats where the receiver experiences rapid motions, acceleration ordeceleration, the combination of the magnet and the ferrite switchinglayer provides an additional benefit that the attraction between themagnet and the layer provides a magnetic attraction that can keep thedevice from unnecessary slipping during motion and this may be quiteadvantageous.

In any of the examples given above, the ring magnet and its variationsincluding the gap are described only by way of example. In accordancewith other embodiments, it is also possible to achieve the same or asimilar effect with use of any appropriate one or several permanentmagnets or electromagnets of arc, disc, cylinder, square, rectangular,triangular, oval, or ring, etc. shape, magnetization orientation andmagnetic flux density pattern. As described above, it is important tooptimize the type and structure of the material and the DC switchingmagnetic field appropriately to achieve optimum saturation. The use ofanisotropic or multi-layer switching layer also provides furtherflexibility and design possibilities. Since a particular type of magnetand field strength may be required to open the aperture (in conjunctionwith the magnetic layer), it is therefore unlikely that a casual oraccidental placement of a magnet by a user will open this aperture.Furthermore, if such an aperture is opened, the system with receivercommunication and/or feedback can be designed to require a communicationsignal to verify presence of a receiver and continue providing power.Therefore, the systems described here can be implemented in an extremelyrobust and safe manner.

For ease of illustration, the switching layer was described above as onelayer in many of the above descriptions. In accordance with variousembodiments, such as for manufacturing and/or performance reasons, itmay be desirable for the switching layer to be actually made of multipleactive layers. For example, the FineMET® sheet material may compriseone, two or more layers of active Ferromagnetic material sandwichedbetween adhesive or backing layers. This is done to accommodate the thinnature of the basic manufactured layer while providing sufficientperformance and overall active layer thickness. In general, the multiplelayers of the switching layer (sheet or material) of soft and/or hardmagnetic material may be similar or different to improve performance andcharacteristics. Interesting and useful effects may be achieved by usingexchange coupling between the layers as used in magnetic recordinglayers.

It is also possible to operate a receiver designed for tightly coupledoperation in a Magnetic Coupling configuration as described earlier.Since tightly coupled systems contain resonant circuits in the receiver,by appropriate design of the charger and the magnetic layer, positionfree operation of the tightly coupled receiver such as a WPC receiver onan MC charger is possible.

An additional observation is that in the MA configuration, with areceiver containing an appropriate magnet placed on the charger surface,the magnetic aperture is opened as described above. The inventors haveexperimentally observed that a second receiver (with or without magnet)placed on top of the first receiver at distances of an inch or moreapart from the first receiver coil also receives substantial amount ofpower if no or minimal shielding is incorporated behind the firstreceiver's coil. In accordance with an embodiment, the amount of powerreceived is larger than received by a receiver coil placed at such adistance from the charger surface when a magnet placed near the surfaceopens an aperture. This is an indication that, in accordance with someembodiments, the coil and/or circuit from the first receiver (close tothe charger surface) acts as a resonant repeater as described earlierand the second receiver coil (from the receiver not requiring a magnetfarther away and above the first receiver) can be designed to interactand resonate to extend the power to larger distances from the surface.This important and useful effect demonstrates that, in accordance withvarious embodiments, multiple receivers can be stacked (possibly toseveral receivers and many inches high) from the charger surface and allthe receivers may be powered and or charged simultaneously. It alsodemonstrates that once a magnetic aperture is opened, the power from theaperture can be effectively guided or extended far above the chargersurface. By using smaller or larger dimension coils along this path, themagnetic field physical dimension can be expanded or contracted as in acolumn of power from the aperture. By use of different coil turns anddimensions, different power levels and/or voltages can be extracted fromthis column at different positions.

The system described here, thus provides a 3-dimensional power outletthat allows the user to extract power at different locations on thesurface and vertically above the charger surface. Interesting and usefulapplications of this approach for powering products or powerdistribution can be envisioned. Such a system may also be used within anelectric or electronic product to distribute different power or voltagesto different locations.

For example, it would also be possible to develop multi-voltage and/ormulti-power power supplies where different vertically stacked powerreceiver coils extract the appropriate power and voltage from a commonprimary (charger) coil. For fixed power supplies (where the receiverdoes not need to be physically removed), use of a switching layer maynot be necessary since the x-y dimension flexibility is not required.Thus a charger coil and multiple vertically stacked receiver coils maybe used.

In accordance with some embodiments, it may not be desirable to have themagnetic field extend beyond the first receiver. As described earlier,use of appropriate ferromagnetic, shielding, and/or metal layer behindany of the receiver coils can suppress this field reducing any potentialeffect of the magnetic radiation on nearby devices, objects, or livingtissue. So the field extending in the z direction can be manipulated notto produce undesirable results. In accordance with some embodiments, itmay also be possible to route the magnetic field past sensitive partsand have it then extend beyond the device to the next device withoutaffecting the parts to be shielded. For example, in the case a chargerfor multiple mobile phones is developed that allows stacking of thephones on the charger, the first receiver coil and magnet closer to themobile device would open the aperture in the charger and provide powerto the first receiver. This can be followed by a structure of ferriteand/or metal layer that protects the sensitive electronics of the mobilephone or any metal layers from the magnetic field but routes it abovethe first mobile device or phone to reach a second device's receivercoil and power that and so on and so forth, thus simultaneously poweringmultiple stacked mobile devices and yet shielding the electronics insidethem.

While the above description is provided for the MA configuration, italso applies to the MC configuration or a combination of MA and MCchargers and receivers can be combined.

As described earlier, in accordance with an embodiment, the charger canbe implemented so that it is able to decode and implement multiplecommunication and regulation protocols and respond to themappropriately. This enables the charger to be provided as part of amulti-protocol system, and to operate with different types of receivers,technologies and manufacturers.

To implement this, at the initial stage, the Charger may send out a pingsignal at a frequency that is known to be able to power the multipletypes of protocols in existence and then “listen” for a response. If thefrequency range of the potential types of receivers is very wide (e.g.from kHz to MHz) it may be necessary to change the resonant frequency bychanging the coupling capacitor. For example, the system may be designedso that a number of resonant capacitors such as C1 in FIG. 2 areconnected through switches in between the drive circuit and the coil sothat the resonant condition can be changed over a wide range. Thecharger can switch in a capacitor and couple to the coil through thatcapacitor, apply power (ping), listen for a response or check forcurrent draw due to a receiver and if no response is detected, move toswitch in another capacitor, apply power (ping), look for a response,etc. to ensure all possible protocols and possible receiver types havebeen interrogated.

As shown in FIG. 10, in one protocol, after the receiver sends back acommunication signal back to the charger, in response to it, the chargeradjusts its frequency (to get closer or further from resonance and powertransferred) and then awaits further information from the receiver. Thereceiver acknowledges the change and as shown in the second data packetin the receiver signal, has modified its state and communicates back tothe charger. This closed loop continues during the charging process.

One of the issues in developing multi-protocol systems is that theoperating frequency of the different systems and protocols may besufficiently different (e.g. from kHz to MHz) that the charger systemmay not achieve resonance with the receiver in the frequency rangepossible with the charger coil and the resonant capacitor used andtherefore efficient operation with the receiver nearby can't beachieved. To solve this problem, the system may be designed so that anumber of resonant capacitors such as C1 in FIG. 2 are connected throughswitches in between the drive circuit and the coil so that the resonantcondition can be changed over a wide range. One method to overcome thisis shown 560 in FIG. 43 where to achieve larger operating frequencyrange, the charger may contain a series of capacitors (C1 . . . Cn) andswitches (S1 . . . Sn) under microcontroller control MCU1 to switch inand out the appropriate values of resonant capacitance in series orparallel to the charger coil inductance L1 to have a resonant frequencyin the range appropriate for different protocols. In idle condition withno receiver nearby, the charger MCU1 may periodically power up andsequentially connect the appropriate capacitance value through S1 to Snswitches and then start powering the coil L1 by switching the AC switchS at the appropriate ping or interrogation frequency. If an appropriatereceiver is nearby and is powered by the charger, it would respond backand the signal can be detected by the current detection and demodulationcircuit in the charger and appropriate action can be taken by MCU1 toverify and/or continue charging/apply power at the appropriate powerlevel by changing the switching frequency and/or duty cycle, and/orchanging the input voltage level to the switch S which is switchedrapidly to generate the switching frequency. If no response is received,either no receiver is nearby or it operates at a different protocol orfrequency and the Charger MCU would proceed to check for a receiver at adifferent protocol or frequency by interrogating at a differentfrequency range or if necessary, switching in a different or additionalcapacitor before proceeding with the ping as described above. Thecharger would continue interrogation/pinging at different protocolsuntil a receiver responding to one is found to be nearby and then movesto apply power appropriately and based on decoding the signal pattern ofthe receiver to proceed with the appropriate algorithm/protocol tocontinue power application.

FIG. 44 shows the system of FIG. 43 implemented in a resonant Converterarchitecture 570. The microcontroller MCU1 adjusts power to the coil L1by adjusting Vin, the frequency, or duty cycle of the generated ACvoltage or a combination thereof and generate the desired signal byswitching Q1 and Q2 transistors. MCU1 also controls switches S1 throughSn to connect appropriate resonant capacitors to achieve a wide range ofresonant frequencies. It must be noted that in a charger with differentsections to charge different devices as shown in FIGS. 40 and 41, thedifferent sections can operate at different frequencies or protocols asdescribed above since they are independent.

In addition or instead of changing the resonant capacitor, it may bealso possible to have different charger coils that are constructed ofPCB or wire or Litz wire or a combination of such coils and havedifferent turns, diameters, number of layers, construction, etc. in theentire charger pad or a subsection of the charger that can be switchedin and out of the electrical path in the charger to achieve optimumpower or communication coupling between the Charger and Receivers ofdifferent protocol, voltage, or power levels The added cost of inclusionof such additional coils or capacitors and possibly the extra complexityin the Firmware in the Microcontroller may be quite small but allow muchmore flexibility and interoperability with different receivers ofdifferent protocol, power, or voltage in these cases.

The same procedure or a subset of this can also be adopted for caseswhere communication is accomplished by other means than communicationthrough coil such as RF or optical, etc. or in cases where differentfrequencies and also communication paths (through coil, through optics,and/or through RF) are employed in the different protocols. In thismanner a multi-protocol architecture that is adaptable to many systems,powers, and/or voltage levels can be implemented.

Alternately, the receiver can be designed or implemented to accommodatedifferent types of chargers or be multi-protocol. For example, once areceiver is awakened by a charger, it can try to detect the ping or theoperating frequency used by the charger. This can be done by any numberof phase locking or other frequency detection techniques. Alternately,the receiver can send back a variety of trial communication signalsduring ping process to establish which type of device is performing theping. Once the type of the charger is established, the receiver canproceed and communicate with the appropriate communication protocol andfrequency with the charger.

Another advantage of an architecture such as FIG. 39(c) and FIG. 39(d)or FIG. 40 and FIG. 41 is that in the position free systems (looselycoupled and magnetic aperture) the power transfer efficiency of a systemin general decreases with the surface area of the charger. It may betherefore advantageous to subdivide a large area charger into smallersections and by detecting the receiver's placement on this sectionthrough in coil or separate coil communication, RF, mechanical, optical,magnetic or weight detection, etc. and only activate the section where areceiver is placed to enable higher efficiencies or output powers. Ofcourse this can be combined with verification, etc. to provide furthersecurity and safety in these conditions.

FIG. 45 shows a geo-cast architecture 580 (similar to FIG. 39(c) andFIG. 39(d) where a number of charger power and/or communicationsub-units are connected through a multiplex system to the coil or coilsin each section and can be connected to each section to supportreceivers placed in each. In a variation of this with multiple sub-unitsdriving a single or multiple coils in a single section, multiplereceivers may also be charged or powered in each section. To implementthis architecture effectively, it may be necessary to have multiplecoils of the same or dissimilar pattern cover the same area of a sector.For example, multiple coils patterns of shape shown in FIG. 12 or othershape/size can be stacked on top of each other under the charger topsurface and connected to the multiplexer so each can be individuallydriven. Each coil may be designed to have different number of turnsand/or shape or pattern to be more advantageous for powering differentreceiver types (protocols), powers, and/or voltages. Each of the coilsmay be driven at a different frequency and operate one at a time orsimultaneously to provide power to one or more receivers placed in thatsector with different protocols, power, or voltage levels. It must benoted in magnetic coupling or magnetic aperture charger geometries thatthe charger AC magnetic field generated in the magnetic/switching layerwould be an addition of the magnetic fields from different driversand/or coils and/or frequencies and while all receivers with appropriateresonance and/or magnets or other parts would sense the AC magneticfield in the magnetic/switching layer, only receivers that are designedto operate at a particular frequency range or tuned to that frequencyintentionally would have power coupled out to them. Thus an individualvirtual path (channel) for power transfer and/or communication betweenthe appropriate sub-unit and receiver would exist. Inclusion of aparallel or series resonant capacitor in the receiver and tuning wouldenhance this strong dependency on the frequency and enable suchindependent channels to operate simultaneously.

In addition, in such architectures, it is possible to increase theamount of power delivered to a device in any section by multiplexingpower from sub-unit drivers or operating multiple coils in that section(displaced vertically—i.e. stacked; or laterally—i.e. side by side)simultaneously to increase the AC magnetic field in that section. Inorder for this addition from multiple coils to add constructively, itmay be necessary to keep the phase of the sub unit drive circuits inphase with each other. This can be easily achieved by controlling thecontrol signal to the drive circuit from the microcontroller in thecharger (MCU1).

Moving to architectures where higher degrees of flexibility in thepositioning is achievable, FIG. 46 shows possible architectures for fullpositioning freedom 600. FIG. 46(a) shows a charger which broadcastspower to a number of receivers placed anywhere on its surface. In thesimplest case, the charger may broadcast power in an open loop geometryto one or more receivers which may or may not regulate the receivedpower and deliver it to a load. Presence of one or more loads near or onthe charger can be detected by the charger being brought into resonanceby presence of one or more receivers and an increase in input current.Techniques such as periodic pinging of power can be used to detect thepresence of receivers. In more controlled architectures, the receiverand or the receiver in combination with the charger establish some formof communication and control protocol to control and/or regulate theoutput power, voltage, or current from each receiver. In the case shownin FIG. 45(a), all receivers operate with the same protocol and requirethe same voltage and power level. In FIG. 46(b), the charger powers orcharges multiple receivers that may operate in different protocols,and/or have different voltage and/or power requirements. FIG. 46(c) Inthis architecture, different sub-units and/or coils in the charger poweror charge receivers with different protocols, voltage and/or powerlevels placed anywhere on a charger. And finally in FIG. 46(d), eachsub-unit and/or coil in the charger is responsible for up to onereceiver on the charger. Each sub-unit and/or coil may bemulti-protocol, support different voltages, and/or powers. The maximumnumber of receivers that can be powered or charged on a charger is thesame as the number of sub-units.

It must also be noted that it is possible to provide a system that canoperate in any of the modes shown in FIG. 39 as well as a mode orarchitecture in FIG. 46. For example, it may be possible to have acharger that contains 3 sets of coils and drivers and communicationsub-units configured to operate as in FIG. 39(d) to provide charging forup to 3 receivers operating in different voltages, powers, or protocolssimultaneously with each receiver being limited to a certain surfacearea of charger only (similar to shown in FIG. 39) so no more than onereceiver can be placed in each area. At the same time, the charger canfor example have a large coil covering the entire or majority or asection of the charger surface that allows the charger to simultaneouslyor at different times power one or many receivers operating in adifferent protocol placed at any location on the charger such as in FIG.46(a) or FIG. 46(b) by broadcasting power and receiving it on thisparticular type or types of receivers. This may be achieved by havingdifferent coils and/or power driver/communication circuits power thedifferent parts or multiplexing the same coil and/or powerdriver/communication circuit to function in the different modes. In anembodiment, the 3 coils to achieve the operation for mode shown in FIG.39(d) (Multi-protocol Geo-cast) are in one physical layer behind thecharger top surface and/or the magnetic switching layer and the coil orcoils to achieve the mode shown in FIG. 46(a) or FIG. 46(b) are inanother layer. These may be PCB, wire, or a combination of PCB and wirecoils. The 2 modes mentioned here are only by way of example. Obviously,even more simultaneous modes of operation or different modes allowingsimultaneous interoperability or support for many modes of operation arepossible.

In accordance with an embodiment, to implement the architectures in FIG.46, a number of methods for communication and/or regulation of power canbe used.

In many wireless power/charger systems, it is desired to control theoutput power, voltage, or current from a receiver. In many cases wherethe receiver is used to power or charge a device, it is necessary tokeep the output voltage constant as the impedance of the device changes.In other cases where the output is used to charge a battery, it may bebeneficial to adjust the output voltage in a pre-determined orpre-programmed manner as the impedance of the battery is changed. FIG. 8is an example of such a charging profile. To achieve such a result, aregulator comprising buck, boost, buck-boost, flyback, or linear typecan be incorporated into the receiver output stage. In order to operateefficiently, it is desirable for any wireless charger system to bedesigned so that as the output current is reduced (higher loadresistance), the input power draw by the charger and the output power ofthe receiver is reduced. It is found that in many cases, a higher loadresistance (lower output current), shifts the resonance curve of thesystem (output voltage or power vs. Frequency) to the lower frequency.In such cases, especially for systems where the frequency and/or dutycycle of the charger power signal is not changed during charging, thesystem must be operated at frequencies higher than the resonance peak sothat as the battery connected to the receiver is charged and the currentdrawn decreases, less power is delivered by the receiver and also drawnfrom the input power source to the charger avoiding unnecessaryheating/over voltage at the receiver regulator and efficient operationthroughout the charging profile.

In addition, the output voltage of the receiver coil may be measured andits value or the difference between its value and the desired value maybe reported to the charger to adjust one or many parameters such asvoltage, duty cycle, and/or frequency of the charger signal to bring thevoltage from the coil to within an acceptable range. Methods for suchcommunication and control have been described earlier. However, such aclosed loop may not be able to provide rapid adjustment of the power totransients and the optional output regulator stage can provide anotherlevel of regulation to provide faster performance. FIGS. 2, 3, 4, 6, 42,43, and 44 show systems where this optional output regulator stage isincluded. In an embodiment here with a multi-receiver system such asarchitectures shown in FIG. 46 and developed with loosely coupled ormagnetic coupling or magnetic aperture technology, a regulation stage inthe receiver can be used to provide the output power to the device orbattery. This regulator may or may not be in addition to anycommunication, active feedback and/or control to control the output fromthe receiver coil to the regulator. Systems such as shown in FIG. 46(a)or FIG. 46(b) may use such a regulation in the receiver to provideappropriate output power to devices and batteries.

In a multi-receiver system such as shown 610 in FIG. 47, presence of onereceiver may also influence the power delivered to other receivers. Thiseffect has been observed previously (Zhen Ning Low, Joaquin JesusCasanova, and Jenshan Lin, Advances in Power Electronics, Volume 2010,PP 1-13) where 2 receivers were connected directly to individualvariable resistors and the individual and combined performance of thepower transfer was studied. In the above references, it was noted thatthe power delivered to one receiver was not affected by another receiverplaced on a loosely coupled charger as long as the load resistance forthe second receiver was greater than a certain value (40Ω in this case).In this method, the input impedance of the receivers is designed to behigh to allow operation of the system with no or minimal interferencebetween 2 or more receivers. Using regulators in the output stage tocontrol the output power, it is necessary to select the appropriateregulator and design the overall system so that the interaction due topresence of multiple receivers is minimized or eliminated. Loss ofefficiency due to the regulation stage can be minimized by usingswitching regulators that can have very high efficiencies. In addition,any inductor for the switching regulator can be similarly integratedinto the printed circuit board of the receiver or on the magneticmaterial used for the shield or another magnetic component in thereceiver to provide lower cost, smaller size, or further integration.

Furthermore, the receivers can communicate with the charger by in-band(modulating the power signal such as load modulation) or out of band(Separate RF, optical or other) communication and can be uni-directionalor bi-directional. This communication can validate the receivers,provide info about the power requirement, output voltage, power,temperature, state of charge, foreign object detection (metal in betweencharger and receiver) or other fault conditions. The charger can act onthis info by adjusting the overall power transmission frequency, dutycycle or voltage input to the switching stage to bring the overalloutput to a range to provide sufficient power to the multiple receivers.The charger can also decide to terminate charge, declare a faultcondition or take other actions.

For example, if in-band communication is used, this can be achieved byload modulation as described earlier or through a separate RF, opticalor other method. To avoid collision between messages being sent fromdifferent receivers acting independently and transmitting messages to acharger, the interval between message transmission packets from thereceiver can be pre-programmed to be random, semi-random, or have apattern to allow the charger to be able to distinguish between messagesfrom each receiver without confusion about its origin or corruption ofthe message. If two messages from 2 receivers are received by a chargerat the same time, it can ignore the messages and wait for the nexttransmission from those receivers until a valid transmission isreceived.

As described above, charger surfaces with sizes of up to 18×18 cm withloosely coupled, Magnetic Aperture or Magnetic Coupling technology havebeen tested and provide high efficiencies and power transfers tomultiple receivers. In certain applications, it may be desirable to haveeven larger charger areas, for example, a full table top or surface(such as kitchen counter, etc.) that is fully active and can charge orpower multiple devices placed anywhere on its surface. To enable such anembodiment and retail high efficiency, uniformity, or power transfer, itmay be necessary to use multiple charger sections 620 as shown in FIG.48 that are tiled to be adjacent or overlapping to provide a continuousactive surface. In cases that some gap between the charger coils exist,if the receiver coil area is larger than this gap, the existence of thegap would not pose a non-uniformity problem. The sections may be drivenby one charger, in parallel by one charger circuit or by multiple drivecircuits or have a multiplexer that connects charger circuits possiblywith even different protocols or power levels to different sections asneeded.

Another method of regulating the output voltage of a wireless chargerreceiver has recently been demonstrated by Seong-Wook Choi and Min-HyongLee, ETRI Journal, Volume 30, PP 844-849. In FIG. 49 a simplified system630 for wireless transmission of power with constant output voltage isshown. A capacitor C2 is added in parallel in the charger. The system isoperated at slightly higher frequency than the resonance at an optimumfrequency that can be calculated. With the optimum frequency determined,the value of C2 can be optimized to minimize the current in the chargercoil and optimize transfer efficiency. It can be shown that by choosingthe values of capacitors C1, C2 and C_(r) appropriately, constantvoltage V₁ regardless of the load value can be obtained. The outputstage regulator and/or switch are optional and are anothersafety/reliability measure that can be added if needed. For cases wherethe output is charging a battery directly, the output regulator wouldprovide the necessary output voltage profile for the particular type ofbattery as for example shown in FIG. 8 earlier. In the simple geometryshown in FIG. 49, no communication and/or feedback between the receiverand charger is assumed. Optionally, the charger may include a means ofmeasuring the current through the charger coil and using it to determinethe number of receivers on the charger or presence of a receiver orfault conditions. An optional microcontroller detects this current andcontrols the drive circuitry.

The optimum frequency in the geometry above is dependent on the couplingcoefficient between the charger and receiver coils and therefore the gapbetween the charger and receiver coil. In practice a system that is morerobust may be needed. Presence of multiple receivers may also requireadjustment of the frequency or other operating conditions of the system.Furthermore, fault or end of conditions or other information may need tobe relayed back to the charger. FIG. 50 shows a system 640 that issimilar to the system of FIG. 49 but with a simplified communication andfeedback channel added. Such a system may provide more functionality anda closed loop system in addition to the inherent design to provideconstant voltage V₁ regardless of coupling coefficient variations andaffects of coil to coil distance, etc. therefore providing a more robustsystem.

In cases where direct communication or control and/or regulation betweenthe receiver and charger are necessary or desired (such as architecturesin FIG. 46(c) and FIG. 46(d), this may be achieved by using a differentfrequency and/or charger or receiver coil to provide separatecommunication and/or power channels to individual receivers and/orgroups of receivers. In addition, such techniques and/or FrequencyDivision Multiplexing (FDM) may be used to communicate and/or powerdevices using different protocols or no protocols at all (where thereceiver does not communicate and receives power passively when placedon a charger). As shown in FIG. 47, one or more charger units operatingat same or different frequencies can drive one or multiple charger coilsthat may cover the same physical area or cover different distinctregions of the charger surface. In the receiver, by closing theappropriate switch S_(r1) to S_(m), the receiver can tune to receivepower from the power and/or communication channel for itself or itsgroup of receivers. In the charger, the communication back from eachreceiver or types of receivers is demodulated at a different frequencyof its communication or in a Time Division Multiplexed method andregulation or adjustment of power or other changes to power ortermination for that device or group of device is carried out. While inFIGS. 43, 44 and 47, adjustment of resonant frequency by changing of thecapacitor is shown, any change to impedance of the charger or receivercircuit would provide a shift in the optimum charging frequency as shownin FIG. 14. It is therefore possible to use inductive or capacitivecomponents in the charger and receivers to shift the optimum powertransfer frequency.

In U.S. Patent Application Nos. 2008/0211478, 2007/0109708, and2008/0247210, methods for regulation of output power that depend oncharger and/or receiver based regulation are described. The main methodused (shown 650 in FIG. 51) introduces a variable inductor in parallelto the charger and/or receiver coil that can be optimized to adjust thefrequency and/or phase of the power transfer to the output stage. Thecurrent through the inductor is adjusted by a phase and voltagedetection and control circuit to adjust the control voltage to thetransistor gates and use the transistors to adjust the current throughthe variable inductor and regulate the output. Similar performance maybe achieved by using a variable capacitor.

In an embodiment described here, the inductance in the receiver and/orcharger is adjusted by using multi-tap coil(s) (with PCB or Litz wirecoil) and by adjusting the length of the coil used and therefore therelated inductance (as well as the coupling between the receiver andcharger coils) by connecting or disconnecting switches to change theresonance condition of the system and therefore control the outputpower. Thus regulation of the output power could be realized by thereceivers or chargers. In particular, it would be beneficial to performthe regulation completely by the receivers individually andindependently.

It can be readily appreciated that in the above descriptions manygeometries and systems have been described. In practice, one or severalof these systems can be used in combination in a charger and/orreceivers to provide the desired performance and benefits.

The above description and embodiments are not intended to be exhaustive,and are instead intended to only show some examples of the rich andvaried products and technologies that can be envisioned and realized byvarious embodiments of the invention. It will be evident to personsskilled in the art that these and other embodiments can be combined toproduce combinations of above techniques, to provide useful effects andproducts.

Some aspects of the present invention can be conveniently implementedusing a conventional general purpose or a specialized digital computer,microprocessor, or electronic circuitry programmed according to theteachings of the present disclosure. Appropriate software coding canreadily be prepared by skilled programmers and circuit designers basedon the teachings of the present disclosure, as will be apparent to thoseskilled in the art.

In some embodiments, the present invention includes a computer programproduct which is a storage medium (media) having instructions storedthereon/in which can be used to program a computer to perform any of theprocesses of the present invention. The storage medium can include, butis not limited to, any type of disk including floppy disks, opticaldiscs, DVD, CD-ROMs, microdrive, and magneto-optical disks, ROMs, RAMs,EPROMs, EEPROMs, DRAMs, VRAMs, flash memory devices, magnetic or opticalcards, nanosystems (including molecular memory ICs), or any type ofmedia or device suitable for storing instructions and/or data.

The foregoing description of the present invention has been provided forthe purposes of illustration and description. It is not intended to beexhaustive or to limit the invention to the precise forms disclosed.Many modifications and variations will be apparent to the practitionerskilled in the art. The embodiments were chosen and described in orderto best explain the principles of the invention and its practicalapplication, thereby enabling others skilled in the art to understandthe invention for various embodiments and with various modificationsthat are suited to the particular use contemplated. It is intended thatthe scope of the invention be defined by the following claims and theirequivalence.

What is claimed is:
 1. A system for use in charging and/or powering oneor more devices and/or batteries by wireless power, comprising: one ormore components including a ferromagnetic, ferrite, or other magneticmaterial or layer, which are used to modify the magnitude and/or phaseof an electromagnetic field in one or multiple dimensions.
 2. The systemof claim 1, wherein the ferromagnetic, ferrite, or other magneticmaterial or layer is provided within one or more wireless chargers orpower supplies and/or the electronics, coils, magnetic material, ormagnets therein, and/or one or more wireless power receivers and/or theelectronics, coils, magnetic materials, or magnets therein; and used incharging or powering the one or more devices and/or batteries.
 3. Thesystem of claim 1, wherein the one or more components including theferromagnetic, ferrite, or other magnetic material or layer is used toprovide a degree of position independence in charging or powering theone or more devices and/or batteries.
 4. The system of claim 1, whereinthe modifying the magnitude and/or phase of the electromagnetic field inone or multiple dimensions includes locally modifying the properties ofthe ferromagnetic, ferrite, or other magnetic material or layer so thatit acts as a switching layer, allowing a transmitter coilelectromagnetic field to be preferentially transmitted through a locallymodified area.
 5. The system of claim 1, wherein the ferromagnetic,ferrite, or other magnetic material or layer includes one or morematerials selected from the list consisting of soft iron, silicon steel,laminated materials, silicon alloyed materials, powder iron, hydrogenreduced iron), carbonyl iron, ferrites, vitreous metals, alloys of Ni,Mn, Zn, Fe, Co, Gd, and Dy, nano materials, ferrofluids, magneticpolymers, or similar materials or combination thereof.
 6. The system ofclaim 4, wherein the locally modified area of the switching layer iscreated by saturating or altering the magnetization curve of theferromagnetic, ferrite, or other magnetic material or layer locally onor near where the receiver coil is placed.
 7. The system of claim 6,wherein the saturating or altering the magnetization curve of theferromagnetic, ferrite, or other magnetic material or layer locally isprovided by saturating or modifying the permeability of the layerthrough application of one or more DC and/or AC magnetic field such as apermanent magnet or electromagnet or local application of heat or acombination thereof.
 8. The system of claim 7, wherein the permanentmagnet and/or electromagnet is incorporated behind, in front, around orat the center of the receiver and/or charger coil or a combinationthereof such that it has sufficient magnetic field to saturate or alterthe magnetization curve of the ferromagnetic, ferrite, or other magneticmaterial or layer locally on or near where the receiver coil is placed.9. The system of claim 7, wherein the permanent magnet or electromagnetincludes one or more disc, square, rectangular, oval, curved, ring, orother shape of magnet and combination thereof or a multi-pole magnet andwith appropriate magnetization orientation and strength that can providesufficient DC and/or AC magnetic field to shift the operating positionof the magnetization curve, so that the combination of the transmittercoil, the affected ferrite or ferromagnetic or magnetic material orswitching layer and the receiver coil move to a resonance condition at agiven frequency for power transfer.
 10. The system of claim 1, furthercomprising one or more additional components or features to improve theperformance or usability of the system in charging or powering one ormore devices and/or batteries by wireless power.